Updated COVID-19 boosters are available right now, and the recommendations for who should get one have expanded since many people last checked. In the fall of 2024, the FDA authorized reformulated mRNA vaccines targeting newer variants, and the Advisory Committee on Immunization Practices (ACIP) recommended additional doses for adults 65 and older and for immunocompromised individuals as young as six months. The landscape has shifted from a single annual shot toward a more tailored approach, and the details matter more than the headlines suggest.
Who Is Eligible for a Booster Right Now
The current booster recommendations split people into a few groups. If you are 65 or older, ACIP recommended a second dose of the 2024–2025 COVID-19 vaccine, to be given at least six months after your first 2024–2025 dose, with a minimum interval of two months. If you are between six months and 64 years old and moderately or severely immunocompromised, you are also recommended to get that second dose on the same schedule. People in that immunocompromised category can actually receive three or more total doses of the 2024–2025 vaccine, based on a conversation with their doctor about the risks and benefits.1PubMed Central. Use of Additional Doses of 2024–2025 COVID-19 Vaccine for Adults Aged ≥65 Years and Persons Aged ≥6 Months with Moderate or Severe Immunocompromise
For children, the picture is evolving. The American Academy of Pediatrics has recommended vaccination for all infants and children ages 6 through 23 months, for immunocompromised children ages 6 months through 18, and for children ages 2 through 18 in certain higher-risk groups, including those who live in long-term care or congregate settings, have never been vaccinated, or share a household with someone at high risk of severe COVID.2PubMed. Recommendations for COVID-19 Vaccines in Infants, Children, and Adolescents, 2026-2027: Technical Report
For healthy adults under 65 who are not immunocompromised, the standard recommendation is a single updated dose for the current season. That said, if you have not received any COVID vaccine in over a year, you are further behind than you might realize, and a single updated dose still provides a meaningful bump in protection.
What Is in the Current Boosters
The 2024–2025 COVID-19 vaccines were reformulated to target newer branches of the Omicron family tree. The FDA authorized vaccines based on the KP.2 variant, while the European Medicines Agency went with JN.1.3PubMed Central. Immunogenicity of JN.1 and KP.2 COVID-19 mRNA vaccines against emerging SARS-CoV-2 variants These represent a substantial jump forward from the XBB.1.5 formula used in the 2023–2024 round, which itself was a big update from the original Wuhan-based shots. Both Pfizer and Moderna produce mRNA versions, and Novavax offers a protein-based alternative.
Updating the vaccine strain matters. A large analysis of 56 cohorts from 16 studies found that boosting with a more recently matched vaccine produced antibody levels roughly 40% higher against the next circulating variant, compared to boosting with an older formula. That advantage held even after accounting for how many prior shots and infections someone had already experienced.4Nature Communications. Predicting COVID-19 booster immunogenicity against future SARS-CoV-2 variants and the benefits of vaccine updates
The reason these updates are necessary is that newer variants escape the antibodies generated by older vaccines. Studies of the previous Omicron-targeted boosters showed this clearly: neutralization dropped sharply against each successive subvariant, with JN.1 showing the most resistance. Sera from people who got the Moderna Omicron booster had substantially weaker neutralizing activity against JN.1 compared to earlier Omicron subvariants, and the Pfizer Omicron booster showed a similar steep decline.5Vaccine: X. Neutralizing antibody responses to SARS-CoV-2 variants after COVID-19 vaccination and boosters That pattern of immune escape is the whole reason we keep updating the formula.
How Well Do the Current Boosters Work
Effectiveness data for the 2024–2025 vaccines against hospitalization is encouraging, especially for preventing the worst outcomes. A study from the VISION and IVY networks estimated that the updated vaccines reduced COVID-related emergency department or urgent care visits by about a third among adults 18 and older. For immunocompetent adults 65 and older, effectiveness against hospitalization was roughly 45–46%. For immunocompromised adults in that same age group, it was around 40%.6Morbidity and Mortality Weekly Report. Interim Estimates of 2024–2025 COVID-19 Vaccine Effectiveness Among Adults Aged ≥18 Years — VISION and IVY Networks, September 2024–January 2025
A separate analysis of immunocompetent adults found overall effectiveness of about 40% against hospitalization, but that number climbed steeply with the severity of the outcome: roughly 46% against needing supplemental oxygen, about 49% against acute respiratory failure, 60% against ICU admission, and 79% against mechanical ventilation or death. In other words, the sicker you would otherwise get, the more the vaccine pulls its weight.7JAMA Network Open. Estimated Effectiveness of 2024-2025 COVID-19 Vaccination Against Severe COVID-19
An earlier look at the KP.2 subvariant vaccines in a case-control study showed effectiveness of about 68% against hospitalization, higher than the XBB.1.5 vaccines that preceded them, which pooled at around 46–50% against hospitalization in adults.8PubMed. Updated Evidence for Covid-19, RSV, and Influenza Vaccines for 2025-2026 None of these numbers approach the sky-high effectiveness seen in the first months after the original vaccine rollout, but the virus and population immunity have both changed dramatically since 2021.
For immunocompromised individuals specifically, a second booster has shown real-world benefit against the most dangerous outcomes. A nationwide study in South Korea found that a second booster dose in immunocompromised people and long-term care residents was associated with about 57% effectiveness against critical infection and 63% against death, compared with those who had only received one booster.9PubMed Central. Effectiveness of Second mRNA COVID-19 Booster Vaccine in Immunocompromised Persons and Long-Term Care Facility Residents
Why Protection Fades and Boosters Become Necessary
The case for repeated boosters rests on a well-documented biological pattern: antibody levels from COVID vaccination drop significantly in the months after a shot. In a longitudinal cohort in Bangladesh, anti-spike antibody titers fell by roughly half within the first several months after vaccination across all vaccine types tested, then continued declining at each subsequent check-in.10Scientific Reports. Antibody longevity and waning following COVID-19 vaccination in a 1-year longitudinal cohort in Bangladesh
A more detailed picture comes from a three-year tracking study of immune responses after vaccination. It found that antibody levels dropped sharply, about fivefold, in the first weeks to months after vaccination. After that initial plunge, levels stabilized at a much lower plateau. The researchers described this as a two-phase decay: a rapid drop driven by short-lived antibody-producing cells, followed by a steady state maintained by longer-lived immune cells.11Immunity. Longitudinal analysis of immune responses to SARS-CoV-2 infection and vaccination over 3 years That plateau is real protection, but it may not be high enough to prevent infection with a drifted variant, which is where boosters come in.
The good news is that your immune system does not start from scratch each time. T cells, which are critical for controlling an infection once it takes hold, respond differently than antibodies. Research shows that T cell responses plateau after the first couple of doses and remain stable through subsequent boosters, without signs of exhaustion or functional impairment.12PubMed Central. Evolution of SARS-CoV-2 T cell responses as a function of multiple COVID-19 boosters T cells also cross-recognize different variants more effectively than antibodies do, meaning they provide a broader safety net even when circulating strains have drifted away from the vaccine strain.13Cell Reports. Long-term dynamics of T cell and antibody responses to repeated COVID-19 mRNA boosters and asymptomatic infections
The Immune Imprinting Question
One issue researchers have been tracking closely is immune imprinting, sometimes called “original antigenic sin.” The concept is that your immune system tends to lean on memories from its first encounters with a virus, even when a newer vaccine is trying to teach it about a different variant. After the XBB.1.5 monovalent booster, studies found that the neutralizing antibody response was still heavily dominated by memory B cells originally trained against the Wuhan-Hu-1 spike, the strain from the very first vaccines.14PubMed Central. Persistent immune imprinting occurs after vaccination with the COVID-19 XBB.1.5 mRNA booster in humans
This does not mean boosters fail. They clearly raise antibody levels against the updated variant. But the degree of improvement can depend on your vaccination history. In one study, people who had skipped the earlier bivalent booster showed a bigger fold-increase in neutralizing antibodies after the XBB.1.5 booster than those who had received every available dose. Against the EG.5.1 variant, for example, those who skipped the bivalent saw about a 31-fold boost versus a 7-fold boost in those who had not skipped. The final absolute antibody levels after vaccination were similar between groups, but the jump was more dramatic in the less-vaccinated group, suggesting that accumulated immune imprinting somewhat dampens the relative boost from each successive shot.15Communications Medicine. Immune imprinting and vaccine interval determine antibody responses to monovalent XBB.1.5 COVID-19 vaccination
For a practical standpoint, this is not a reason to skip future boosters. The endpoint that matters most is where your antibody levels land after vaccination, not how steep the climb was. But it does explain why vaccine designers keep pushing for formulas that better redirect the immune response toward currently circulating strains.
Can You Get It at the Same Time as a Flu Shot
Yes, and the evidence is reassuring. A randomized trial of the Moderna COVID booster co-administered with a seasonal flu vaccine found that the immune responses to both vaccines were non-inferior to giving them separately. The antibody responses to all four flu strains and to the COVID spike protein met the pre-specified criteria for equivalence. Side effects, mostly injection-site pain and muscle aches, were similar whether the shots were given together or apart.16PubMed Central. No immunological interference or concerns about safety when seasonal quadrivalent influenza vaccine is co-administered with a COVID-19 mRNA-1273 booster vaccine in adults
The Pfizer COVID vaccine showed the same pattern when co-administered with an inactivated flu vaccine: immune responses met non-inferiority criteria for both vaccines, and serious adverse events were reported in fewer than 1% of participants, with none considered vaccine-related.17PubMed Central. Safety and Immunogenicity of the BNT162b2 Vaccine Coadministered with Seasonal Inactivated Influenza Vaccine in Adults One study actually found that getting the COVID and flu vaccines at the same time produced slightly higher and more durable spike-specific antibody responses than getting them separately.18PubMed Central. Concurrent administration of COVID-19 and influenza vaccines enhances Spike-specific antibody responses So there is no immunological reason to schedule separate appointments.
Timing After a Recent Infection
If you recently had COVID, the standard guidance is to wait at least a few months before getting boosted. The biological rationale is straightforward: a recent infection has already revved up your immune system, so the booster’s added benefit is smaller if you get it right away, and waiting allows your immune memory to mature in a way that makes the next vaccine dose more effective.
A large cohort study found that the timing of first vaccination relative to a prior infection made a substantial difference in how long people stayed protected against reinfection. Those who waited at least six months after infection before starting vaccination had significantly longer intervals before reinfection than those vaccinated earlier. The effect was consistent across incomplete, complete, and booster regimens. People who received an early incomplete regimen actually had a doubled risk of reinfection compared to unvaccinated individuals, while those who waited and received a booster regimen had the lowest reinfection risk, reduced by at least 80% compared to unvaccinated people.19Scientific Reports. Impact on the time elapsed since SARS-CoV-2 infection, vaccination history, and number of doses, on protection against reinfection
Boosters and Long COVID
Protection against long COVID is one of the less-discussed benefits of staying boosted. A systematic review found that booster vaccination was associated with a significantly lower risk of developing long COVID, with a pooled odds ratio of 0.74 compared to unvaccinated individuals.20Nature Communications. A systematic review and meta-analysis of the impact of vaccination on prevention of long COVID Another systematic review looking at vaccination before infection found odds ratios for developing long COVID that ranged from 0.22 to 1.03 with one dose and 0.25 to 1.02 with two doses, with three doses showing the strongest effect.21PubMed Central. Effect of covid-19 vaccination on long covid: systematic review
A study from southeastern Brazil sharpened this picture further: among people infected during the Omicron period, only those who had received two booster doses showed a significant reduction in long COVID risk compared to those with just a primary series. A single booster dose was not significantly protective in that analysis.22PubMed. Protective effect of a second booster dose against long COVID among individuals infected with SARS-CoV-2 in southeastern Brazil The takeaway is that more recent and more frequent vaccination appears to do a better job of lowering your odds of persistent symptoms after infection.
The Protein-Based Option
Not everyone wants an mRNA vaccine, and Novavax’s protein-based shot (NVX-CoV2373) remains available as an alternative. In a phase 3 trial, it produced robust antibody responses when used as a booster regardless of what vaccine someone had originally received, with strong reactivity even against immune-evasive Omicron subvariants.23PubMed. Immunogenicity and safety of NVX-CoV2373 as a booster: A phase 3 randomized clinical trial in adults
There is a tradeoff. A comparative study found that people boosted with NVX-CoV2373 had lower spike-specific antibody titers and neutralizing antibody levels than those boosted with mRNA vaccines, and the protein-boosted group saw higher rates of new infections during the study period. On the other hand, they reported fewer side effects, and cellular immune responses were similar between the groups.24PubMed. Immunogenicity and safety of heterologous booster with protein-based COVID-19 vaccine (NVX-CoV2373) in healthy adults For people who experienced significant side effects from mRNA shots or who prefer a more traditional vaccine technology, the protein-based option is a reasonable choice, though the antibody response may be somewhat lower.
Why So Many People Have Not Gotten One
Despite the availability of updated boosters, uptake has been low. The reasons are not mysterious. A study on message fatigue found moderately high levels of COVID-related communication burnout among vaccinated people in the United States. That fatigue was directly associated with lower likelihood of getting a booster and lower intentions to get one, independent of other factors like perceived risk or belief in vaccine effectiveness.25PubMed. Message Fatigue and COVID-19 Vaccine Booster Uptake in the United States
A Canadian evidence brief catalogued the most common reasons people give for skipping boosters: worry about side effects (both short and long-term), unease about receiving multiple doses from different manufacturers, doubt that an additional dose offers meaningful extra protection, a general sense that too many doses are being asked for, and the belief that a previous infection makes the booster unnecessary.26PubMed Central. COVID-19 after the pandemic Evidence brief on facilitators, barriers and hesitancy of COVID-19 booster doses in Canada Some of these concerns are understandable but not well supported by the evidence. Prior infection does offer protection, but as described above, it wanes and is boosted substantially by vaccination. Mixing vaccine brands has been studied extensively and shown to be safe. The effectiveness data against severe outcomes remains solid, particularly for older adults.
Nasal Vaccines on the Horizon
One development that could change the booster landscape is intranasal vaccines. Unlike injected vaccines, nasal vaccines can stimulate mucosal immunity directly in the airways where the virus first lands. By triggering secretory IgA antibodies in the nasal passages, these vaccines could potentially prevent not just severe disease but infection and transmission as well.27PubMed Central. COVID-19 intranasal vaccines: current progress, advantages, prospects, and challenges Several candidates are in clinical development worldwide, and India has already authorized one for use. Whether these eventually replace or supplement injected boosters remains to be seen, but they address a gap that current vaccines largely do not: blocking the virus before it gets past your nose.