Fall & Winter 2026: Your Respiratory Vaccine Guide

PRIMARYMD  |  SCIENCE BRIEF  |  NO. 1

The short version

This week, JAMA published three independent reviews covering roughly 300 recent studies on COVID-19, influenza, and RSV vaccines. I reviewed those findings and the key original studies behind them. My conclusion: these vaccines continue to meaningfully reduce the risk of hospitalization and other serious outcomes, particularly for older adults and people with underlying health conditions. Another year of safety monitoring also identified no new concerns.

Here is what I recommend:

• Everyone 6 months and older: Get a flu shot, ideally in late September or October.
• Age 65 or older: Get an enhanced flu vaccine and the updated COVID-19 vaccine.
• Age 75 or older: Get one RSV vaccine if you have not already received one.
• Age 50–74 with a condition that increases your risk: Get the updated COVID-19 vaccine and talk with us about RSV vaccination. Relevant conditions include chronic heart, lung, kidney, or liver disease; diabetes; obesity; and a weakened immune system.
• Under 65 and healthy: Get a flu shot. The updated COVID-19 vaccine is reasonable and remains your choice. RSV vaccination is not currently recommended for most people in this group.
• Already received an adult RSV vaccine: Do not repeat it this year. It is currently a one-time dose, not an annual vaccine.

All three vaccines can be given during the same visit. Most importantly, you do not need to determine on your own which category fits you. Your PrimaryMD team will review your age, health history, medications, recent infections, and previous vaccine reactions and tell you exactly what we recommend for you.

Your fall vaccine checklist.  Do = we recommend it.  Consider = a reasonable choice; the benefit depends more on your individual risk factors and preferences.  Not yet = not currently recommended for your group.

* Enhanced formulation means high-dose Fluzone, adjuvanted Fluad, or recombinant Flublok. Any of the three is appropriate.   † Risk conditions vary somewhat by vaccine but may include heart, lung, kidney, or liver disease; diabetes; obesity; cancer; a weakened immune system; frailty; or residence in a long-term-care facility. The COVID-19 risk list is particularly broad.

Timing essentials

• Your simplest plan: one vaccination visit in late September or October covers all three. Not sure which row applies to you? Send us a message and we will give you a personalized recommendation.
• Recently had COVID-19? Waiting approximately three months before the updated vaccine may be reasonable.
• Before going to the pharmacy: confirm it has the specific vaccine or formulation you need, is in network, expects it to be covered, and does not require a prescription. If you hit a snag, contact us before giving up.

The rest of this brief explains the evidence behind these recommendations.

Dear PrimaryMD member,

“Do I really need all these shots?” It is a fair question, and you deserve a nuanced answer, especially when federal vaccine guidance has been in more flux than at any point in history.

This week, JAMA published three systematic reviews—one each for COVID-19, influenza, and RSV—from the Vaccine Integrity Project, an independent group of academic epidemiologists and former CDC leaders. The researchers screened nearly 20,000 publications from the past year, selected roughly 300 that met their standards, and evaluated each for its risk of bias. I read all three reviews and returned to the original trials behind the most important findings. What follows is my assessment of what the evidence shows, where uncertainty remains, and what I recommend.

Why we look beyond the “bad week”

Most people think of the flu, COVID-19, or RSV as a miserable week followed by a return to normal. For many people, that is exactly what happens. But what we want you to understand is what a severe inflammatory illness can do to the rest of the body—sometimes after the fever and respiratory symptoms have resolved.

Infection and the heart

When the immune system mounts a major response to an infection, it can destabilize plaque in the arteries, make the blood more prone to clotting, and place additional strain on the heart. A landmark study of people with laboratory-confirmed influenza found that the risk of a heart attack was roughly six times higher during the week after infection than during the year before or after it (Kwong et al., New England Journal of Medicine, 2018). Large studies of COVID-19 survivors have found elevated rates of heart attack, stroke, heart failure, and blood clots for up to a year after infection—including among people who were never hospitalized (Xie et al., Nature Medicine, 2022).

The encouraging side is that preventing or reducing the severity of an infection may also reduce some of its cardiovascular consequences. In a pooled analysis of randomized trials, flu vaccination reduced major cardiovascular events by approximately one-third among people with heart disease (Behrouzi et al., JAMA Network Open, 2022), and a trial that vaccinated patients shortly after a heart attack found lower rates of death and repeat heart attacks during the following year (Fröbert et al., Circulation, 2021). Newer RSV evidence points in the same direction: in a Medicare study of more than 15 million adults 65 and older, RSV vaccination was estimated to be 79% effective at preventing heart attacks, strokes, and blood clots occurring alongside an RSV infection (Wiegand et al., 2026), and in a Danish randomized trial of 131,000 adults over 60, the vaccinated group experienced fewer hospitalizations for cardiorespiratory illness (Lassen et al., JAMA, 2025).

Infection and the brain

Among older adults who survived severe sepsis—the body’s overwhelming response to an infection—the rate of new moderate-to-severe cognitive impairment was approximately three times higher than among similar adults who had not experienced that illness (Iwashyna et al., JAMA, 2010). Studies following people after COVID-19 have also documented measurable cognitive changes, with more pronounced effects after more severe illness. The overall direction of the evidence is consistent: a major inflammatory illness can have effects that continue after the initial infection appears to be over.

These studies do not prove that every respiratory vaccine will prevent every cardiovascular or cognitive event. They do support a consistent conclusion: the consequences of a serious respiratory infection can extend well beyond the lungs, and reducing the risk or severity of that infection may protect more than we traditionally associate with a vaccine.

How to read the numbers in this brief

You will see numbers such as “53% effective” throughout this brief. Vaccine efficacy—or effectiveness—is a relative measure: it tells us how much a vaccine reduced a particular outcome compared with not being vaccinated. It does not mean that 53% of vaccinated people were completely protected while the remaining 47% received no benefit. The percentage must also be connected to a specific outcome—infection, symptomatic illness, hospitalization, intensive care, or death—because vaccines generally provide stronger and more durable protection against severe illness than against becoming infected at all.

Consider the original trial of Pfizer’s RSV vaccine, Abrysvo, which randomly assigned approximately 34,000 adults over age 60 to vaccine or placebo and followed them through an RSV season.

The 67% relative reduction tells us how much less frequently the outcome occurred in the vaccinated group. The absolute reduction tells us how much difference the vaccine made among the particular people enrolled—relatively healthy adults with an average age of approximately 67. An 80-year-old with heart or lung disease begins with a much higher chance of being hospitalized with RSV, so a similar relative reduction could translate into a substantially greater absolute benefit. This is the logic behind our recommendations: the value of vaccination depends not only on how well the vaccine performs, but also on your underlying likelihood of experiencing the outcome it is designed to prevent.

Three more points will help you interpret the evidence that follows:

• The outcome matters. In the same trial, efficacy was 67% against lower-respiratory illness and 86% against more severe illness. This pattern—stronger protection against worse outcomes—appears across the vaccines discussed in this brief.
• The range around an estimate matters. A result written as “67% (29–86)” means the true effect is reasonably likely to fall within that range. A very wide range means the estimate is less precise, usually because relatively few events occurred.
• The type of study matters. Randomized trials provide the strongest evidence that the vaccine itself caused the difference. Real-world studies can include far more people but are more vulnerable to differences between those who choose to be vaccinated and those who do not.

Throughout this brief: Randomized trials show = the strongest evidence of a causal effect. Real-world studies suggest = useful evidence, with more potential for bias. Our interpretation = how we connect the evidence to your individual risks and the decision in front of you.

RSV: the newer vaccine for older adults

If you are over 50, you may still think of RSV—respiratory syncytial virus—as primarily a childhood infection. It is also a significant cause of winter hospitalization among older adults. The risk rises sharply with age and is higher among people with chronic heart or lung disease, kidney or liver disease, complicated diabetes, severe obesity, immune suppression, or frailty. Until 2023, there was no RSV vaccine available for adults. There are now three: Arexvy from GSK, Abrysvo from Pfizer, and mResvia from Moderna. The first two use more traditional vaccine technology; mResvia is an mRNA vaccine.

What the evidence shows

Randomized trials show: In the original Abrysvo trial, the vaccine reduced lower-respiratory illness by 67% and more severe illness by 86% during the first RSV season. A more recent Danish trial involving 131,000 adults over age 60—the largest randomized adult vaccine trial of which we are aware—found the vaccine 83% effective against RSV hospitalization. The effect appeared similar among participants with heart or kidney disease, although those subgroups were too small to estimate as precisely.

Real-world studies suggest: Protection is strong during the first season and decreases over time. In a study of 576,000 US veterans, effectiveness against RSV hospitalization was approximately 81% during the first six months and 49% at 12 to 18 months; a CDC hospital network estimated 69% during the season of vaccination and 58% across two seasons. One study estimated 72% effectiveness against admission to intensive care over 18 months. Among people with weakened immune systems, estimates were lower and less precise, ranging from approximately 30% to 73%.

My critical read

• The vaccine works against the outcome that matters most. An 83% reduction in RSV hospitalization in a randomized trial involving 131,000 people is unusually strong evidence.
• Protection appears to decline over time. Researchers are still studying whether and when another dose may eventually be helpful. For now, RSV vaccination is a single dose—not an annual vaccine.
• There is a rare safety signal worth noting. FDA’s post-marketing analysis estimated approximately nine additional cases of Guillain-Barré syndrome per million Abrysvo doses and seven per million Arexvy doses among adults 65 and older. FDA added a warning to both products while noting that the evidence remains insufficient to establish that the vaccines caused the additional cases. For someone with a meaningful chance of RSV hospitalization, the expected benefit is much larger than this rare potential risk; for a healthy person at lower risk, the calculation is less one-sided. That is why the recommendation is universal beginning at age 75 but tied to individual risk between ages 50 and 74.
• Immune suppression complicates—but does not reverse—the decision. Someone with a weakened immune system may receive less protection from the vaccine, but that same person is also more likely to be hospitalized with RSV. In many cases, we will still recommend vaccination as one part of a broader prevention plan.

What I recommend

• Age 75 or older: Get one dose if you have not previously received an adult RSV vaccine. This is the clearest RSV recommendation.
• Age 50–74 with a condition that increases your risk: Get one dose. Relevant factors include chronic heart or lung disease, chronic kidney disease, complicated diabetes, chronic liver disease, severe obesity, moderate or severe immune suppression, certain neurologic conditions that affect breathing or airway clearance, frailty, and residence in a nursing home.
• Age 50–74 and otherwise healthy, or under age 50: Not routinely recommended at this time, even though some products have received FDA approval for certain higher-risk younger adults. Pregnancy is a separate indication: Abrysvo may be recommended between 32 and 36 weeks of pregnancy during RSV season to protect the infant.
• Already received an RSV vaccine? Do not receive another dose this year. Otherwise, late summer through early fall—generally August through October—provides the greatest benefit before RSV begins circulating widely.

COVID-19: the updated 2026–27 vaccine

First, the numbers that put the decision in context. During the 2024–25 season, COVID-19 caused an estimated 290,000 to 450,000 hospitalizations and 34,000 to 53,000 deaths in the United States, and approximately 88% of those deaths occurred among people age 65 and older. Estimated annual hospitalization rates were approximately 933 per 100,000 adults age 75 and older, 274 per 100,000 at ages 65–74, and 105 per 100,000 at ages 50–64—so the annual risk for a 78-year-old was roughly nine times that of a 55-year-old. COVID-19 is less dangerous than it was during the earliest years of the pandemic, but it remains a consequential virus for older adults and people with underlying health conditions.

The updated 2026–27 vaccines target XFG, a descendant of the JN.1 lineage. Available products include the mRNA vaccines Comirnaty from Pfizer-BioNTech and Spikevax and mNEXSPIKE from Moderna, as well as Nuvaxovid from Novavax, a protein-based option for people who prefer a non-mRNA vaccine. Approved ages and eligibility vary by product.

What the evidence shows

There are no longer placebo-controlled trials of updated COVID-19 vaccines in adults; with effective vaccines and other forms of immunity already widespread, a long-term placebo group would be difficult to justify ethically or practically. The evidence therefore comes from real-world studies. Real-world studies suggest:

• Among adults age 65 and older, last season’s updated vaccine reduced COVID-19 hospitalization by 53% in one CDC hospital network and by 59% in a separate study of approximately 1.2 million people. Across eight studies of vaccines used since the JN.1-era formulas began in 2023, estimates ranged from approximately 35% to 59%.
• Protection was generally stronger against the worst outcomes: approximately 57% against intensive care admission and 73% against mechanical ventilation or death among older adults, and 52% to 79% against death from COVID-19 across four studies.
• Among adults under age 65, one study estimated 54% protection against hospitalization, although the wide range around that estimate reflected greater uncertainty; other adult studies reported approximately 20% to 55%. Among people with weakened immune systems, protection was lower but still present: approximately 23% to 36% against hospitalization, and 32% to 53% against critical illness among patients receiving dialysis.
• Evidence beyond hospitalization is encouraging but less definitive. Health care workers who had received three to five vaccine doses were less likely to develop long COVID than those who had received two, and vaccinated people who became infected were less likely to transmit the virus to household members.
• Timing matters. Measured across an entire respiratory season, protection against hospitalization averaged approximately 35%; measured about six weeks after vaccination, it was approximately 53%. Protection is strongest during the first few months and then gradually declines.

How to understand the current guidance

FDA determines which vaccine products may be used and for whom: this season’s vaccines are approved for adults age 65 and older and for younger people with at least one condition that increases the risk of severe COVID-19. CDC guidance currently uses “individual decision-making” rather than making the same recommendation for every person. We do not read that wording as meaning the evidence is unclear or that vaccination is no longer recommended. The evidence remains strongest for older adults, people with underlying health conditions, people with weakened immune systems, and pregnant patients; for healthy younger adults, the expected benefit is smaller, so individual priorities play a larger role. The list of qualifying conditions is broad—obesity, diabetes, heart disease, high blood pressure, kidney or liver disease, asthma and other lung diseases, cancer, immune suppression, smoking, and several other physical and mental health conditions—and many adults who think of themselves as generally healthy meet at least one.

If you have not received a COVID-19 vaccine recently

Immunity declines over time after both vaccination and infection. Protection against severe disease lasts longer than protection against infection, but after a year or more it is meaningfully reduced—particularly among older adults. You generally do not need to “catch up”: for most adults, one dose of the current formula is the recommended schedule regardless of how many prior seasonal doses were missed. If you recently had COVID-19, it may be reasonable to wait approximately three months before vaccination.

My critical read

The evidence is observational rather than randomized, so every individual estimate has limitations. But the consistency across different health systems, seasons, vaccine formulas, and study designs is more persuasive than any single number: updated vaccination repeatedly reduces hospitalization, with stronger protection against intensive care, mechanical ventilation, and death. The benefit is greatest among people whose starting risk is highest. Waning protection makes timing important; it is not evidence that vaccination provides no benefit. For a healthy younger adult, the absolute benefit is smaller, which makes vaccination a genuine preference-sensitive decision rather than a universal imperative.

What I recommend

• Age 65 or older: Get the updated vaccine, ideally in September or October. The risk-benefit balance strongly favors vaccination.
• Under age 65 with a condition that increases your risk: Get the updated vaccine.
• Pregnant: We recommend updated COVID-19 vaccination because pregnancy increases the risk of severe illness and vaccination also provides some protection to the infant after birth.
• Under age 65 and otherwise healthy: Consider it. Vaccination remains a reasonable choice, particularly if you live with or care for someone vulnerable, have frequent exposure to other people, want to reduce your likelihood of long COVID, or simply want to lower the chance of losing a week to illness.

On the safety of mRNA vaccines

We know some members have questions about mRNA technology, including claims they may have encountered online. The latest evidence adds another year of research to an already extensive safety record, built from hundreds of millions of doses and multiple independent monitoring systems.

• No new safety concerns were identified. The latest review examined myocarditis, heart attack, Guillain-Barré syndrome, low platelets, stroke, blood clots, seizures, pregnancy outcomes, and other serious events. A U.S. Veterans Affairs analysis of approximately 1.65 million vaccinated veterans likewise found no increased risk across 48 prespecified conditions.  [2026 JAMA evidence review]
• Myocarditis is a real but rare risk, concentrated in specific groups. It has occurred most often in adolescent and young adult males, generally during the first week after vaccination and particularly after a second mRNA dose. FDA labeling estimates approximately 27 cases per million doses among males ages 12–24, compared with approximately eight per million across people ages six months through 64. Symptoms typically improve within several days, although the longer-term significance of some persistent imaging findings remains uncertain. The risk is considerably lower in older adults, and spacing doses farther apart may reduce it.  [FDA prescribing information]
• The pregnancy data remain reassuring. In a study of approximately 140,000 pregnancies, vaccination was not associated with an increased risk of stillbirth, preterm birth, or infants who were small for gestational age.  [CDC pregnancy guidance]
• The most common trade-off is a rough day or two. A sore arm, fatigue, headache, fever, or muscle aches are common and usually resolve within one to three days. Severe allergic reactions can occur but are rare, which is why vaccination sites are prepared to recognize and treat them.  [CDC safety guidance]
• The vaccine cannot alter your DNA. The mRNA delivers temporary instructions outside the cell nucleus, where DNA is stored. After those instructions are used, the cell breaks down and removes the mRNA.  [CDC explanation of mRNA vaccines]

My critical read

No medical intervention is completely risk-free, and “no new safety signal” does not mean that every possible rare event has been ruled out. It means that the known risks are increasingly well characterized, no new pattern of serious harm emerged in the updated review, and monitoring continues. The identification of myocarditis is an example of that process working: a rare, age-specific risk was detected, quantified, publicly disclosed, and incorporated into labeling and vaccination guidance.

What I recommend: For members whose age or health conditions place them at greater risk from COVID, the established safety profile of mRNA vaccines supports vaccination. The balance may be different for younger, lower-risk members or anyone with a history of myocarditis, pericarditis, a severe allergic reaction, or another significant vaccine reaction.

Influenza: still the workhorse, with two important updates

Last season was a difficult one. The CDC estimates that influenza caused 390,000 to 800,000 hospitalizations and at least 24,000 deaths. Flu vaccination must be repeated annually because the circulating viruses change and protection fades over time. It also has the strongest evidence of the three vaccines in this brief for reducing cardiovascular complications.

What the evidence shows

Flu vaccination continues to reduce hospitalization and death. During the 2025–26 season, vaccination reduced flu-related hospitalization by approximately 31% in adults 65 and older and 29% in younger adults. That was a relatively modest year but within the usual range, which varies depending on how well the vaccine matches the circulating strains. Among older adults, recent estimates of protection against death from influenza ranged from approximately 29% to 66%.  [2026 JAMA evidence review]

For adults 65 and older, high-dose vaccine provides better protection than standard-dose vaccine. In a randomized trial of more than 332,000 older adults followed over three flu seasons, the high-dose vaccine prevented approximately 44% more flu-related hospitalizations than the standard-dose vaccine. There is an important caveat: the difference was much smaller when researchers used the broader outcome of hospitalization for either flu or pneumonia, because many cases of pneumonia are unrelated to influenza. Our interpretation is straightforward: high-dose vaccine is clearly better at preventing severe influenza, but it is not a substitute for a pneumonia vaccine.

The safety record remains reassuring. A study of nearly 10 million people vaccinated during the 2023–24 season found no increased risk of Guillain-Barré syndrome, anaphylaxis, stroke, or encephalitis.

What’s new: the first mRNA flu vaccine

In August, the FDA approved Moderna’s MFLUSIVA, the first mRNA influenza vaccine, for adults 50 and older. In a trial of approximately 40,700 adults, it prevented about 27% more laboratory-confirmed flu illnesses than a standard-dose flu vaccine. The trade-off was more short-term discomfort: reactions severe enough to interfere with daily activities occurred in 6.4% of MFLUSIVA recipients compared with 1% of those receiving the conventional vaccine, while vaccine-related serious adverse events were similarly rare in both groups (three versus two).  [FDA approval letter]

There are two important limitations. MFLUSIVA was compared with a standard-dose vaccine, not with the enhanced vaccines already recommended for older adults. In addition, its approval for adults 65 and older was based partly on antibody responses, with a direct trial against high-dose vaccine now required to confirm its clinical benefit in that age group.

My critical read

Even in a modest season, flu vaccines meaningfully shift the odds away from hospitalization and death. MFLUSIVA is a promising new option for adults 50–64. For adults 65 and older, we recommend staying with a high-dose, adjuvanted, or recombinant vaccine until direct comparative evidence gives us a reason to change.

What I recommend

• Everyone six months and older: Get a flu vaccine, ideally in September or October. Vaccination later in the season is still worthwhile if you miss that window.
• Age 65 or older or anyone immunocompromised: Ask for an enhanced formulation: high-dose Fluzone, adjuvanted Fluad, or recombinant Flublok. Any of the three is appropriate. If none is available when you are there, getting another age-appropriate flu vaccine is better than delaying indefinitely.  [CDC clinical guidance]
• Age 50–64: Get an age-appropriate flu vaccine. MFLUSIVA is now an FDA-approved option, particularly if you prefer an egg-free vaccine and are comfortable with a greater chance of short-term side effects.
• Egg allergy: No longer a reason to avoid a flu vaccine.

Timing and logistics

For most members, one vaccination visit in late September or October is a practical way to prepare for respiratory-virus season. Flu, COVID-19, and RSV vaccines may be given during the same visit: a study of approximately 2.5 million veterans found no increase in heart attack, stroke, Guillain-Barré syndrome, myocarditis, or blood clots with same-day COVID and flu vaccination, and trials combining RSV with flu, shingles, and pneumonia vaccines have not identified a serious safety concern.  [CDC coadministration guidance] If you would rather separate them, that is also reasonable—there is no required waiting period between these vaccines. A completed set is better than a perfect schedule you never finish.

A sore arm and a day or two of fatigue, headache, muscle aches, or low-grade fever are common and generally short-lived. If you develop symptoms that are severe, unusual, or persistent—or chest pain, shortness of breath, palpitations, or signs of a serious allergic reaction—seek appropriate medical care and let your PrimaryMD team know.

Before going to the pharmacy, run through the checks in Timing essentials. If the pharmacy tells you that you are not eligible, cannot obtain the recommended formulation, or may have to pay unexpectedly, contact us. Please send us the date, vaccine name, and location—or a photo of your record—so we can keep your chart current.

The bottom line: my recommendation

Vaccines are not a guarantee that you will avoid every infection. Their greatest value is in shifting the odds away from severe illness, hospitalization, intensive care, and—potentially—the cardiovascular and cognitive consequences that can follow a serious respiratory infection.

After reviewing the newest evidence, our conclusion at PrimaryMD is clear: these vaccines continue to offer meaningful protection, particularly for older adults and people with underlying health conditions. The risks are not zero, and the benefit is not identical for everyone. But for most members to whom we are recommending vaccination, the trade-off is a sore arm or a short period of feeling unwell in exchange for a meaningfully lower chance of the outcomes that matter most.

Where the recommendation is clear, you may hear from us directly. You are also always welcome to contact your care team—whether you have a condition we did not mention, recently had COVID, experienced a previous vaccine reaction, are unsure which formulation to request, or simply want to talk the decision through.

This is the purpose of the PrimaryMD Science Brief. When important new evidence emerges, we will do the reading, distinguish what is well established from what remains uncertain, and explain what we believe matters for your care.

Sources

Primary sources for this issue

Lipson RA, Senerth E, et al. COVID-19 vaccine effectiveness and safety for the 2026-2027 respiratory season. JAMA. Published online September 2, 2026. doi:10.1001/jama.2026.18191

Senerth E, Sheikholeslamian SM, et al. Influenza vaccine effectiveness and safety for the 2026-2027 respiratory season. JAMA. Published online September 2, 2026. doi:10.1001/jama.2026.18126

Senerth E, Sheikholeslamian SM, et al. RSV immunization effectiveness and safety for the 2026-2027 respiratory season. JAMA. Published online September 2, 2026. doi:10.1001/jama.2026.17871

Walsh EE, Pérez Marc G, et al. Efficacy and safety of a bivalent RSV prefusion F vaccine in older adults (RENOIR). N Engl J Med. 2023;388:1465-1477.

Key studies discussed within those reviews

Lassen MCH, et al. RSV prefusion F vaccine for prevention of hospitalization in older adults (DAN-RSV). N Engl J Med. 2026;394:138-151; and Lassen MCH, et al. RSVpreF vaccine for preventing cardiovascular hospitalizations: prespecified analysis of DAN-RSV. JAMA. 2025;334:1431-1441.

Bajema KL, et al. Durability of RSV vaccine effectiveness among US veterans. JAMA Intern Med. 2026;186:78-88.

Surie D, et al. RSV vaccine effectiveness against hospitalization during 2 seasons. JAMA. 2025;334:1442-1451.

Wiegand RE, et al. Effectiveness of RSV vaccines against RSV-associated thromboembolic events. Emerg Infect Dis. 2026;32:246-249.

Wiegand RE, et al. Interim estimated effectiveness of 2025-2026 COVID-19 vaccines in adults. JAMA Netw Open. 2026;9:e2625152.

Ma KC, et al. Estimated effectiveness of 2024-2025 COVID-19 vaccination against severe COVID-19. JAMA Netw Open. 2026;9:e2557415.

Cai M, Xie Y, Al-Aly Z. 2024-2025 COVID-19 vaccine and outcomes in US veterans. N Engl J Med. 2025;393:1612-1623.

Asomaning K, et al. Three-year safety assessment of BNT162b2 in the Veterans Health Administration. Vaccine X. 2026;29:100791.

Xie Y, Choi T, Al-Aly Z. Adverse events after same-day COVID-19 and influenza vaccination: a target trial emulation. Ann Intern Med. 2026;179:1073-1084.

Kiely M, et al. Safety of COVID-19 vaccines among pregnant individuals in Quebec. BMJ Open. 2025;15:e106494.

Johansen ND, et al. High-dose influenza vaccine effectiveness against hospitalization in older adults (DANFLU-2). N Engl J Med. 2025;393:2291-2302.

Leroux-Roels I, et al. Efficacy and safety of an mRNA seasonal influenza vaccine in adults (FLUENT). N Engl J Med. 2026;394:1803-1813.

Maloney P, et al. Interim estimates of 2025-26 influenza vaccine effectiveness. MMWR. 2026;75:116-123.

Lloyd PC, et al. Safety monitoring following influenza vaccination, 2023-2024. Vaccine. 2025;63:127614.

Additional sources

Kwong JC, et al. Acute myocardial infarction after laboratory-confirmed influenza infection. N Engl J Med. 2018;378:345-353.

Xie Y, et al. Long-term cardiovascular outcomes of COVID-19. Nat Med. 2022;28:583-590.

Behrouzi B, et al. Influenza vaccination and cardiovascular risk: a meta-analysis. JAMA Netw Open. 2022;5:e228873.

Fröbert O, et al. Influenza vaccination after myocardial infarction (IAMI). Circulation. 2021;144:1476-1484.

Iwashyna TJ, et al. Long-term cognitive impairment among survivors of severe sepsis. JAMA. 2010;304:1787-1794.

US FDA. Guillain-Barré syndrome warning for Abrysvo and Arexvy, January 7, 2025; approvals of 2026-2027 formula COVID-19 vaccines, August 27-28, 2026; approval of mFLUSIVA, August 5, 2026.

General health information for PrimaryMD patients; not a substitute for individualized medical advice. Contact your care team with questions about your situation.