Moderna
Ad26: adenovirus type-26; GMT: geometric mean titer; MNA: microneutralization assay; MT: microneutralization titer; ND: not determined; PRNT: plaque reduction neutralization testing; SFCs: spot-forming cells; VNA: virus neutralizing antibody; VP: viral particles; Y: years.
Another important information provided by these phase I/II studies was related to the effect of age. Among studies shown in Table 1 , only studies on BNT 162 b2 and ChAdOx1nCov-19 vaccines included subjects over 65 years of age [5] , [6] , [8] . These studies demonstrated both antigen-binding Ig-G and virus-neutralizing responses in older adults but also a possible decrease in such responses with increasing age [5] , [6] . Nevertheless, an elderly-dedicated phase I study showed that mRNA 1273 vaccine induces a good Ig-G response against the spike-protein as well as significative neutralizing antibody titers in adults older than 70 years of age [8] . Taken as a whole, these results suggested the possibility to demonstrate COVID-19 vaccines’ efficacy in phase III trials.
One of the main issues of phase III trials, particularly in the case of a new pathology, is to define the primary criterion to be used as efficacy markers as well as to define the level of efficacy that will be considered as pertinent. Undeniably, the definition of the primary criterion strongly impacts both the conduct of the trial and the future modalities of prescription of the vaccine. On June 2020, the FDA has released a guidance document for the development and licensure of COVID-19 vaccines [9] . This document stated that symptomatic laboratory-confirmed COVID-19 might be an acceptable primary endpoint for a COVID-19 vaccine efficacy trial with an efficacy level of at least 50% required. Moreover, other secondary criteria might be used to determine the possible efficacy on asymptomatic or severe infections. As a consequence, study sample sizes and timing of interim analyses had to be based on the statistical success criteria for primary and secondary efficacy analyses and realistic, data-driven estimates of vaccine efficacy and incidence of COVID-19 for the populations and locales in which the trials are conducted [9] .
According to these conditions, phase III studies have been conducted in countries where the virus spread was extremely high and have included in a few months several tens of thousands of subjects [10] , [11] , [12] , [13] . According to these studies and except unwanted effects related to usual reactogenicity, these vaccines appear safe. As summarized in Table 2 , among the four vaccines already authorized in Europe the overall efficacy defined as reduction of symptomatic COVID-19 varies from 67% to 95% [10] , [11] , [12] , [13] . These results are largely greater than the minimum efficacy level of 50% required by the FDA [9] . Furthermore, these levels of efficacy are also similar or even higher than that the mean 60% observed with the influenza vaccines [14] . It should be underlined that mRNA vaccines [10] , [11] appear to have a higher efficacy than that of adenoviral vectored vaccines [12] , [13] . Nevertheless, a definitive conclusion about any comparisons should be done with caution. The complexity of the design of ChAdOx1nCov-19 vaccine phase III study does not facilitate neither the interpretation nor any comparisons of data. On the other hand, regarding interim analyses of trials reported in the Table 2 , the protection against severe infection appears to be close to 100% for all vaccines but not for Ad26COVS1 vaccine where data recently published show protection against severe infection with one dose of vaccine of only 77% [13] . It remains to determine how this result is only representative of this vaccine rather than may be finally observed with all other COVID-19 vaccines when long-term follow-up data will be available.
Clinical efficacy observed in phase III studies of the 4 vaccines available in Europe.
BNT 162 b2 BioNTech/Pfizer | mRNA 1273 Moderna | ChAdOx1nCov-19 AstraZeneca/Oxford | Ad26COVS1 Janssen | |
---|---|---|---|---|
Number included in the analysis | 37,706 | 30,351 | 17,178 | 43,783 |
Age | ≥16 y | ≥18 y | ≥18 y | ≥18 y |
Elderly (%) | > 55 y (42.2%) | > 65 y (24.8%) | 56–69 y (10.4%) ≥70 y (5.7%) | ≥60 y (33.5%) |
Doses | 30 μg (days 1/22) | 100 μg (days 1/29) | Several combinations of low and full doses at different times | 5.10 vp (single dose) |
Primary end-point | Symptomatic COVID-19 | Symptomatic COVID-19 | Symptomatic COVID-19 | Symptomatic COVID-19 |
Overall efficacy (95% CI) | 95% (90.3–97.6) | 94.1% (89.3–96.8) | 66.7% [63.1 or 80.7% ] (57.4–74.0) | 66.9% (59.1–73.4) |
Clinical efficacy on variants | ND | ND | B.1.1.7: 70.4% B.1.351: 10.4% | B.1.351: 52% |
Neutralization activity on variants | B.1.1.7 preserved B.1.351 reduced | B.1.1.7 preserved B.1.351 reduced | B.1.1.7 preserved B.1.351 reduced | B.1.1.7 preserved B.1.351 preserved |
Protection against severe infection | 100% | 100% | 100% | 76.7 to 85.4 % |
ND: not determined; VP: viral particles; Y: years.
Some other elements remain to be clarified in real life conditions, namely the effect on mortality, the level of efficacy in the elderly and the clinical efficacy of vaccines according to emerging variants and the duration of protection. Concerning mortality, the studies have not been designed to answer this question, it may then be difficult to bring clear and conclusive result. Moreover, according to the drastic reduction of severe infections observed in vaccinated-people, these studies are probably under-powered to clearly demonstrate the effect of vaccines on mortality.
Regarding elderly, not all published phase III studies had included many elderly people but in studies with a significant number of elderly participants ( Table 2 ), the efficacy level remains relatively close to the one observed in younger subjects (86.4% and 94.7% in people of 65 or over, for mRNA 1273 and BNT 162 b2 respectively) [10] , [11] . Clinical efficacy of vaccines on emerging variants remains also to be more precisely evaluated. Due to the relatively recent emergence of different virus variants’, only few clinical data are available but they show the preservation of ChAdOx1nCov-19 vaccine efficacy on B.1.1.7 variant [15] and a possible decrease in efficacy of both Ad26COVS1 and ChAdOx1nCov-19 vaccines on B.1.351 variant ( Table 2 ) [13] , [16] .
When a new drug comes on the market, it takes usually several years before it could be demonstrated the reproducibility of the phase III clinical trial results’ in real life. Here, according the pandemic situation and the rapid development of mass vaccination campaigns in Israel, USA and UK, we already have many data demonstrating this achievement and also providing supplementary informations. Indeed, as summarized in Table 3 , at least 4 studies that had included 20,000 to more than 1,300,000 vaccinated people provide us impressive results on symptomatic or asymptomatic infections, severe infections as well as on mortality [17] , [18] , [19] , [20] .
Effectiveness of SARS-CoV-2 vaccination in real life.
Settings | Vaccinated population | Vaccine | Symptomatic and asymptomatic infections (95% CI) | Severe infections (95% CI) | Mortality (95% CI) |
---|---|---|---|---|---|
Clalit Health Services Israel | 596,618 | BNT 162 b2 | 92% (88–95) | 92% (75–100) | 84% (44–100) |
Mayo Clinic Health System USA | 31,069 | BNT 162 b2 or mRNA 1273 | 89% (68–97) | 60% (14–79) | None |
Mass vaccination Scotland | 1,331,993 | BNT 162 b2 or ChAdOx1nCov-19 | ND | 91% (95% CI 85–94) 88% (95% CI 75–94) | ND |
Health Care Workers England | 20,641 | BNT 162 b2 or ChAdOx1nCov-19 | 85% (74–96) | None | None |
CI: confidence interval; ND: not determined; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2.
Israel was probably the country which developed the most rapid and extensive mass vaccination campaign in the world by using the BNT 162 b2 vaccine. All people recorded on the Clalit Health Services (53% of Israeli population) who were newly vaccinated during the period from December 20, 2020, to February 1, 2021, were matched to unvaccinated controls according to demographic and clinical characteristics leading to 2 study groups of 596,618 persons each [17] . Looking on results 7 days or more after the second dose of vaccine, symptomatic and asymptomatic as well as severe COVID-19 infections are reduced by 92%. Mortality was also reduced by 84% when regarding 21 to 27 days after the first dose [17] . Even if such results have to be strengthened by a longer-term follow-up, the present study also provides informations about a similar vaccine effectiveness across different age groups and a slightly lower effectiveness among patients with multiple coexisting pathological conditions [17] .
In another paper under review, similar results are provided with the Mayo Clinic Health Database showing a 90% decrease in the development of a symptomatic or asymptomatic COVID-19 infection after BNT 162 b2 or mRNA 1273 vaccination in 31 609 persons [18] . Same kind of results are also provided by both Scotland and England data where both BNT 162 b2 and ChAdOx1nCov-19 vaccines were largely used with evidence of 85% decrease in symptomatic and asymptomatic infections and about 90% decrease in severe infections ( Table 3 ) [19] , [20] . Interestingly, in the Scottish study, such results were observed while the vaccines were administered at only one dose to extend the number of subjects receiving at least one dose of vaccine. Besides the fact that all these data confirm the results of phase III clinical trials, they also help to discuss the question of the effect of vaccine on virus transmission. Because asymptomatic infections are also reduced, it may be that virus transmission is decreased. Moreover, a recently published paper brings supplemental arguments about an effect of vaccines on transmission. Indeed, people who develop a COVID-19 despite vaccination with the BNT 162 b2 vaccine have a clear reduction of viral load that might help to break the spread of the virus [21] . Complementary strategies, such as vaccines able to develop mucosal immunity are also under development [22] .
One of the first questions on hold is the duration of the protection afforded by the vaccination. According to studies follow-up duration, it might be supposed that this protection is as at least 6 to 12 months. This duration will determine the need of a new vaccine boost and possibly the need of annual boost. Some large population-based studies using test-negative designs might help to evaluate these different issues particularly the situations of vaccine failure [23] .
The question of using different vaccines than the one use initially is also crucial. New studies should be designed including studies for the evaluation of the impact of immunogenicity against adenoviral vector if such a vaccine is used for a third injection. Because phase III clinical studies provide no or only few data about immunogenicity, it remains important to also designed studies able to determine more precisely the immune response according to real life administration scheme namely regarding the role of both cellular and innate immunity. Actually, in France, 2 studies are in course to answer such questions by using BNT 162 b2 or mRNA 1273 vaccines in adults including a sub-population of elderly people over 75 years of age.
Besides older people, the question of the efficacy of vaccines in particular populations is also crucial. Several recently published studies bring some answers. To date, there is only few data about the efficacy of vaccine in young people under 18 years of age [10] . Studies evaluating COVID-19 mRNA vaccines in young people aged 12 to 16 years are actually in course but both FDA and EMA have already beenquestioned to provide an authorization of use. On the other hand, COVID-19 mRNA vaccines seem to generate robust humoral immunity in pregnant and lactating women, with immunogenicity and reactogenicity similar to that observed in non-pregnant women [24] . In this study, vaccine-induced immune responses were also significantly greater than the response to natural infection and immune transfer to neonates occurred via placenta and breastmilk [24] . Other data also suggest that a single dose of mRNA vaccine elicits rapid immune responses in SARS-CoV-2 seropositive participants, with post-vaccination antibody titers similar to or exceeding titers found in seronegative participants who received two vaccinations [25] . On the other hand, the immunization rate among kidney transplant recipients who received 2 doses of an mRNA vaccine can be as low as 48% [26] . Very low immune response is evidenced also in others immunocompromised populations. The issue of a third vaccine dose in these non-responsive patients is an intriguing one that will be usefully explored in further research. In this context, a large cohort has been opened in France (COV-POPART) to evaluate the immune response in a number of particular populations including patients with cancer, transplant recipients as well as patients with auto-immune disease receiving immune-modulator treatments.
Last, an important challenge also concerns the efficacy of vaccines regarding the emergence of viral variants [27] . We have previously described some data from clinical trials regarding the decrease or the absence of efficacy of the ChAdOx1nCov-19 namely on B.1.351 variant ( Table 2 ) [12] . Some similar concerns are discussed with the other vaccines but most of the data come from in vitro studies that are not able to consider the possible role of cellular immune response [27] , [28] . Besides to evaluate the effect of a boost particularly with new mRNA sequences, future trials should also explore more precisely the whole immune response against viral variants.
In less than one year, face to a worldwide pandemic due to an unknown virus, several vaccines have been put on the market and have been already used in several tens of millions of people. These vaccines are importantly effective and relatively safe according to the severity of the disease they prevent. Beyond this impressive efficacy of COVID-19 vaccines, notably those based on mRNA, such a technology may first contribute to modify the course of the pandemic but also could bring the world in a new era of specific treatments for numerous pathologies [3] .
The authors declare that they have no competing interest.
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In the first two years of the pandemic, the rate of long Covid was starkly lower among people who were vaccinated, researchers reported.
By Pam Belluck
A large new study provides some of the strongest evidence yet that vaccines reduce the risk of developing long Covid.
Scientists looked at people in the United States infected during the first two years of the pandemic and found that the percentage of vaccinated people who developed long Covid was much lower than the percentage of unvaccinated people who did.
Medical experts have previously said that vaccines can lower the risk of long Covid , largely because they help prevent severe illness during the infection period and people with severe infections are more likely to have long-term symptoms.
But many individuals with mild infections also develop long Covid, and the study, published Wednesday in The New England Journal of Medicine, found that vaccination did not eliminate all risk of developing the condition, which continues to affect millions in the United States.
“There was a residual risk of long Covid among vaccinated persons,” Dr. Clifford Rosen, a senior scientist at the MaineHealth Institute for Research, who was not involved in the study, wrote in an accompanying editorial . Because of that, Dr. Rosen added, new cases of long Covid “may continue unabated.”
The study evaluated medical records of millions of patients in the Department of Veterans Affairs health system. It involved nearly 450,000 people who had Covid between March 1, 2020, and Jan. 31, 2022, and about 4.7 million people who were not infected during that time.
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Covid-19 topics.
For up-to-date information on topics related to COVID-19, visit these U.S. government resources.
Scroll down the page to view all COVID-19 articles, stories, and resources from across NIH. You can also select a topic from the list to view resources on that topic.
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Shining a Light on Long COVID Brain Fog
A new study says the virus seems to be depleting a vital chemical.
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Research finds that SARS-CoV-2 infects coronary arteries and increases plaque inflammation.
Severe COVID-19 May Cause Long-Term Immune System Changes
SARS-CoV-2 Antibodies From Vaccination During Pregnancy May Transfer to Fetuses
Antibodies against SARS-CoV-2 were found in the blood and cord blood of people vaccinated during pregnancy.
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By binding to proteins in the mitochondria, the virus may cause lasting damage to cellular energy production.
Understanding Sleep Problems and Long COVID
Researchers explore whether poor sleep is a cause or result of Long COVID
More Evidence That COVID-19 Vaccination While Pregnant Likely Protects Children
Blood and breastmilk from vaccinated women contain antibodies that may protect infants in first months of life
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Researchers are working with children in Baltimore to learn about student resilience during the pandemic
Measuring the Psychological Distress of COVID-19
People from many racial and ethnic minority groups reported experiencing less distress than White adults
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Many people are reluctant to get vaccinations, often owing to a fear of needles or misinformation about the jabs. Credit: Genaro Molina/ Los Angeles Times /Getty
Vaccines save lives. The measles vaccine alone is estimated to have averted 23 million deaths between 2000 and 2018, according to the World Health Organization (WHO). Data from a subset of countries where girls are vaccinated against the human papillomavirus show that precancerous cervical lesions in girls aged 15–19 plummeted by 51% within a few years of vaccine rollout 1 . Globally, vaccination rates are increasing for many diseases. However, in 2022 (the latest year for which data are available), there were still 14.3 million ‘zero-dose’ children — those who had not received any routine immunizations.
A lack of access to vaccines and the high costs of producing and purchasing them are among the main reasons for low uptake, especially in low- and middle-income countries. In high-income countries, vaccine hesitancy is a significant factor 2 . This is fuelled, in part, by misinformation, which is a problem worldwide 3 .
Countries already have a range of strategies for boosting uptake. All should study the work of researchers who have been evaluating the effectiveness of different interventions. The burgeoning science of vaccine-uptake effectiveness is throwing up some unexpected results that could help public-health authorities to sharpen their policies — and save more lives.
Bird flu in US cows: where will it end?
Take the United States. By October 2022, almost two years after the first COVID-19 vaccines were rolled out, 80% of people in the country aged six months and older had received at least one dose. However, only 33% had received a follow-up booster, which offers the highest possible level of protection against the SARS-CoV-2 virus.
The low booster numbers drove some states to investigate how uptake might be increased. Researchers and health authorities have highlighted ‘last-mile vaccination delivery’ as a major barrier to uptake. In 2021, the White House came up with the idea of encouraging people to get their boosters by offering them free transport to clinics through the ride-hailing companies Lyft and Uber. But a study published in Nature last month 4 shows that this might have done little to increase booster uptake.
Economist Katherine Milkman at the University of Pennsylvania (UPenn) in Philadelphia and her colleagues compared the offer of a free ride with other interventions in a study involving 3.66 million patients of CVS Pharmacy, a retailer that provides vaccination services. The patients, who had all previously been vaccinated against COVID-19, were split into eight groups. One group received a text message offering free transport to the pharmacy; the other seven were sent different text-message reminders to get their boosters.
A global pandemic treaty is in sight: don’t scupper it
People offered free transport were not more likely to get vaccinated than were those who received the other kinds of text message. Messages that had a more positive effect included one proposing an appointment for a day of the week and time of day similar to that of a patient’s previous vaccination, and one informing the recipient that infection rates were high in their county.
“Our article really highlights the importance of testing policy,” says study co-author Sean Ellis, also at UPenn. “Whatever policy we’re putting into place, we should be robustly evaluating whether it actually works, so that if it does work, we can scale it up or continue to do it. And if it doesn’t, we can move on from it and try something else.” In other words, studies are needed to evaluate whether ‘common sense’ interventions actually work in practice.
Researchers are also helping to evaluate the overall effectiveness of text messaging on vaccine uptake. In a study published in May, Hongyu Guan at Shaanxi Normal University in Xi’an, China, and colleagues used the 2021 Chinese General Social Survey, a periodic national survey of households, to examine the actions of 7,281 people. They found that those who received notifications from their local government or community residents’ committees advising them to get vaccinated were twice as likely to get a COVID-19 vaccine than were those who did not 5 .
Half a million children die of malaria every year – finally we can change that
The same study showed that the practice also increased influenza vaccine uptake, albeit from a much lower base. Uptake was more than 40% higher for those notified compared with those who did not receive a text message. This finding builds on the work of earlier studies 6 . However, researchers are less certain whether these approaches are effective for people who are reluctant to be vaccinated 7 .
In low-income countries, research shows that uptake increases when vaccines are taken into communities. In Sierra Leone, for example, the average person lives 3.5 hours away from a vaccination centre and the cost to travel there exceeds their weekly wage. A study published in March 8 found that significantly more people in the country received their COVID-19 vaccines when mobile teams of vaccinators were deployed to 150 rural communities.
Increasing vaccine access and accessibility saves lives, but is only part of the equation. Other interventions are needed to maximize uptake, and these must undergo rigorous testing in different regions and contexts to help health authorities to determine what works. The obvious answer is not always the right one, and the vagaries of human behaviour can thwart seemingly logical solutions.
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On June 27, 2024, the CDC Director adopted the ACIP’s recommendations for use of 2024–2025 COVID-19 vaccines in people ages 6 months and older as approved or authorized by FDA. The 2024–2025 vaccines are expected to be available in fall 2024. This page will be updated at that time to align with the new recommendations. Learn more: www.cdc.gov/media/releases/2024/s-t0627-vaccine-recommendations.html
What to know.
Different types of vaccines work in different ways to offer protection. But with all types of vaccines, the body is left with a supply of “memory” T-lymphocytes as well as B-lymphocytes that will remember how to fight that virus in the future.
It typically takes a few weeks after vaccination for the body to produce T-lymphocytes and B-lymphocytes.
Sometimes after vaccination, the process of building immunity can cause symptoms, such as fever. These symptoms are normal signs the body is building immunity.
Available vaccines.
There are different types of vaccines.
None of these vaccines can give you COVID-19.
COVID-19 vaccines do not affect or interact with our DNA.
To trigger an immune response, many vaccines put a weakened or inactivated germ into our bodies. Not mRNA vaccines. Instead, mRNA vaccines use mRNA created in a laboratory to teach our cells how to make a protein—or even just a piece of a protein—that triggers an immune response inside our bodies. This immune response, which produces antibodies, is what helps protect us from getting sick from that germ in the future.
How mRNA COVID-19 Vaccines Work PDF infographic
Researchers have been studying and working with mRNA vaccines for decades.
Protein subunit vaccines contain pieces (proteins) of the virus that causes COVID-19. These virus pieces are the spike protein. The vaccine also contains another ingredient called an adjuvant that helps the immune system respond to that spike protein in the future. Once the immune system knows how to respond to the spike protein, the immune system will be able to respond quickly to the actual virus spike protein and protect you against COVID-19.
How Protein Subunit COVID-19 Vaccines Work PDF infographic
Protein subunit vaccines have been used for years.
While COVID-19 vaccines were developed rapidly, all steps have been taken to ensure their safety and effectiveness. Bringing a new vaccine to the public involves many steps including:
As vaccines are distributed outside of clinical trials, monitoring systems are used to make sure that COVID-19 vaccines are safe.
New vaccines are first developed in laboratories. Scientists have been working for many years to develop vaccines against coronaviruses, such as those that cause severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). SARS-CoV-2, the virus that causes COVID-19, is related to these other coronaviruses. The knowledge that was gained through past research on coronavirus vaccines helped speed up the initial development of the current COVID-19 vaccines.
After initial laboratory development, vaccines go through three phases of clinical trials to make sure they are safe and effective. No trial phases have been skipped.
The clinical trials for COVID-19 vaccines have involved tens of thousands of volunteers of different ages, races, and ethnicities.
Clinical trials for vaccines compare outcomes (such as how many people get sick) between people who are vaccinated and people who are not. Results from these trials have shown that COVID-19 vaccines are safe and effective, especially against severe illness, hospitalization, and death.
Before vaccines are made available to people in real-world settings, FDA assesses the findings from clinical trials. Initially, they determined that COVID-19 vaccines met FDA’s safety and effectiveness standards and granted those vaccines Emergency Use Authorizations (EUAs). The EUAs allowed the vaccines to be quickly distributed for use while maintaining the same high safety standards required for all vaccines. Learn more in this video about EUAs.
FDA has granted f ull approval for some COVID-19 vaccines. Before granting approval, FDA reviewed evidence that built on the data and information submitted to support the EUA. This included:
These vaccines were found to meet the high standards for safety, effectiveness, and manufacturing quality FDA requires of an approved product. Learn more about the process for FDA approval.
When FDA authorizes or approves a COVID-19 vaccine, ACIP reviews all available data about that vaccine to determine whether to recommend it and who should receive it. These vaccine recommendations then go through an approval process that involves both ACIP and CDC.
Learn more about the Advisory Committee on Immunization Practices (ACIP) and its role in developing vaccine recommendations.
Hundreds of millions of people in the United States have received COVID-19 vaccines under the most intense safety monitoring in U.S. history.
Several monitoring systems continue to track outcomes from COVID-19 vaccines to ensure their safety. Some people have no side effects. Many people have reported common side effects after COVID-19 vaccination , like pain or swelling at the injection site, a headache, chills, or fever. These reactions are common and are normal signs that your body is building protection.
Reports of serious adverse events after vaccination are rare .
COVID-19 (coronavirus disease 2019) is a disease caused by a virus named SARS-CoV-2. It can be very contagious and spreads quickly.
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By Elizabeth Cooney July 17, 2024
V accination lowers the chance of developing long Covid, according to a large new study that also found that the risk of serious complications has diminished but not disappeared as new coronavirus variants emerged.
The study, published Wednesday in the New England Journal of Medicine , compared the health records of more than 440,000 Veterans Affairs patients who were infected with Covid-19 with records of more than 4 million uninfected people. The analysis found that cases of long Covid — also called PASC (post-acute sequelae of severe acute respiratory syndrome coronavirus 2) — fell among all participants during the Delta and Omicron eras of the pandemic, but dropped almost twice as much for vaccinated people when the Omicron variant dominated cases.
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The new data about vaccination’s benefits come during a summer resurgence in Covid cases around the country, and as health officials prepare to roll out a vaccine updated against newer strains that Pfizer and Moderna said they could deliver in August .
“The study is helpful in validating the suspicion that the incidence of PASC decreased over time and in relationship to new variants (this question came up in my clinic just yesterday),” Hilary Goldberg, clinical director of pulmonary and critical care medicine at Brigham and Women’s Hospital in Boston, told STAT in an email. She was not involved in the study. “It is also helpful in validating that vaccination is protective in preventing the development of PASC, a question that has remained somewhat unsettled,” Goldberg said.
In the unvaccinated group, 10.42 out of 100 people early in the pandemic (before vaccines were available) had developed long Covid one year after being infected. In the Delta variant era (defined as June 19 through Dec. 18, 2021), 9.51 out of 100 unvaccinated people were diagnosed with long Covid, compared to 5.34 out of 100 vaccinated people. When the current Omicron era began (Dec. 19, 2021), the gap widened: 7.76 out of 100 unvaccinated people but only 3.5 out of 100 vaccinated people acquired long Covid.
“Vaccines very clearly work, but also clearly, they don’t totally wipe it out,” the study’s senior author, Ziyad Al-Aly, said in an interview. Chief of research at the VA St. Louis Health Care System, he is also a clinical epidemiologist at Washington University in St. Louis. “What we think is really important here is yes, long Covid has declined. But it’s not something that we can completely ignore.”
Earlier studies, including other research from the VA , have hinted at a protective effect for vaccination as well as the harmful impact of severe Covid infections and pre-existing medical conditions on chances of later long Covid. Jai Marathe, an assistant professor of infectious diseases at Boston University and director of the ReCOVer/ long COVID clinic at Boston Medical Center, points out that the new paper says the type or number of comorbidities did not seem to impact PASC.
“From a research perspective, there’s a strong impetus to understand the pathogenesis of PASC, given its constellation of symptoms,” she wrote to STAT. She did not participate in the NEJM paper. “If vaccination alters the immune response, we need to study this further to understand the interplay between viral infection and the immunological changes that contribute to PASC development.”
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Al-Aly hesitates to call this the final word on the full extent to which vaccine coverage better protects people, urging more research. The observational study also describes how symptoms changed with the variants for unvaccinated people.
While debilitating fatigue was once a hallmark of long Covid, more recently gastrointestinal, metabolic, and to a lesser degree, musculoskeletal problems have overtaken fatigue among the unvaccinated, with GI and metabolic issues double the risk of the pre-Delta and Delta periods combined. The study, conducted from March 2020 through January 2022, measured how long Covid does its damage in 10 disease categories: cardiovascular, blood disorders, fatigue, gastrointestinal, kidney, mental health, metabolic, musculoskeletal, neurologic, and pulmonary.
Long Covid risk changed not just with the variants, but also with better hospital treatment, including antivirals, Al-Aly said. Vaccination may have lowered the amount of virus circulating and therefore the risk of long Covid compared to 2020, but that’s only a hypothesis. “Quantitatively, the risk changed dynamically over time, but also qualitatively. It suggests that each strain has its own fingerprints,” he said. “Long Covid is not monolithic.”
Michael Peluso, an infectious disease physician and an assistant professor of medicine at University of California, San Francisco, said he and other doctors may be seeing hints of the changing symptom mix. “It will make me more cognizant of GI and musculoskeletal symptoms in my assessment of long Covid,” Peluso, who was not part of the study, said in an email to STAT. “We certainly see these symptoms, but I would not say that they are the most prominent.
Goldberg wasn’t surprised by the symptom shift. “I find this reassuring in that we would expect the nature of the disease to evolve over time. If we did not see this, we could potentially question the robustness of the data in this analysis.”
To tease out the influence of vaccination versus variant, the study authors used a statistical method called decomposition analysis to conclude that 28% of the lower long Covid incidence in vaccinated people was due to changes in the variants and improved medical care, while attributing 72% of the improvement to the vaccines.
The study did not say how many vaccinations a subject received, Goldberg noted. “Gaps in the data remain — a common question from patients is what is the risk of reactivation or worsening of PASC symptoms from vaccination as compared to from infection,” she said. “We do not have sufficient information to address this question yet, and this question often informs patient decision-making.”
The study’s estimate of long Covid’s cumulative incidence is lower than a June report from the Agency for Healthcare Research and Quality published in JAMA last month that pegged long Covid’s reach at 7% of people who’ve ever had Covid-19. That’s higher than the NEJM paper’s 3% to 4% of adults in the Omicron era, but reflects the agency’s survey results as opposed to the NEJM study’s reliance on health records, Al-Aly said. Estimates of long Covid have swung wildly from early in the pandemic, before agreement was reached on just how to define the condition.
On Tuesday the Centers for Disease Control and Prevention said that people with disabilities face a higher risk of long Covid than people without disabilities. The data said 11% of people with disabilities had long Covid while only 7% of people without disabilities reported symptoms.
In other long Covid research this week, a study published Wednesday in Science Translational Medicine offered an explanation for damage to the lungs that leads to exhausting coughs, lung disease, and shortness of breath. Researchers from the University of Virginia showed that a signaling molecule named interferon-gamma stimulated an abnormal immune response, provoking inflammation and scarring in the lungs after Covid-19 infection. In mice, anti-interferon-gamma antibody treatment reduced inflammation and fibrosis after recovery from their acute infections. Drugs called JAK inhibitors, including one named baricitinib that was granted emergency use for acute Covid-19, “may merit consideration” for treating long Covid, the authors wrote.
Despite progress in research and declines in long Covid cases, the risk is still substantial, Al-Aly and others emphasized.
“Despite the risk of long Covid decreasing, it has not decreased to zero and we will still continue to see many cases of long Covid as SARS-CoV-2 continues to spread,” Peluso said. “This observation is really helpful for clinicians, researchers, and advocates to make the argument that more investment in clinical care and research for long Covid is going to be needed to meet the scope of the clinical need and to ultimately solve the problem.”
Declining uptake of vaccination is concerning, likely due to “Covid burnout,” Marathe said. “Living with a chronic condition like PASC can be debilitating. Therefore, educating and counseling patients and physicians to increase vaccine acceptance is a crucial public health task.”
Goldberg said patients with long Covid often ask her about the risks and benefits of updating their vaccination status. “This study will help to guide those of us caring for patients with PASC,” she said.
Peluso praised the paper’s value for answering questions patients ask “all the time” in clinic. “The risk with Omicron variants may be lower than it was with earlier variants, but it is still significant,” he said. “And being vaccinated is still the best thing someone can do, beyond avoiding Covid, to protect themselves against developing long Covid.”
STAT’s coverage of chronic health issues is supported by a grant from Bloomberg Philanthropies . Our financial supporters are not involved in any decisions about our journalism.
Elizabeth cooney.
Cardiovascular Disease Reporter
Elizabeth Cooney is a cardiovascular disease reporter at STAT, covering heart, stroke, and metabolic conditions.
Coronavirus
public health
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