COVID Boosters in 2026: Less About Hospitals, More About What Comes After

Should I get a COVID booster?

The answer is that it depends on who you are. For healthy adults under 65, the best current evidence comes from a large 2024–25 season study in the New England Journal of Medicine, showing the updated vaccine was associated with approximately 39% effectiveness against hospitalisation and 64% against COVID-associated death across all adults including those under 65. In absolute terms:

These are modest numbers in absolute terms — and the study population was predominantly older and male US veterans, so figures may sit at the higher end for healthy younger adults in NZ.

Protection against symptomatic infection is more modest and fades faster — around 40–50% at peak, declining substantially to roughly 15–30% by four to five months depending on the outcome measured.

For long-COVID risk, observational evidence suggests vaccination is associated with reduced odds. A 2025 systematic review in Nature Communications of 31 observational studies found a pooled odds ratio of 0.74 for booster versus unvaccinated. But the authors explicitly caution that evidence quality is low and residual confounding — health-seeking behaviour, prior immunity — is a genuine limitation. Claims that boosters shorten acute illness duration by a specific number of days are not robustly established yet.

For higher-risk groups (≥65, cardiovascular disease, diabetes, chronic lung disease, immunosuppression, obesity, pregnancy), the benefit–risk calculation is considerably clearer, and additional updated doses are recommended — with timing depending on age and specific risk status.

What are the risks of repeated COVID infections — and can boosters help?

This is the part of the conversation that most healthy adults under 65 are not having — and should be.

Reinfection is not a free pass. A large matched-cohort preprint using US electronic health records from 85 hospital networks (424,616 matched pairs, Omicron era, data through June 2024) found that reinfection resulted in a 35% increase in long-COVID risk compared with a single prior infection (risk ratio 1.35; 95% CI 1.32–1.39), with an absolute risk difference of approximately 2.9 percentage points. This study is pending peer review, though the methodology is robust. The risk was age-graded — smaller in those aged 18–35, larger in the 36–65 group.

A Canadian healthcare worker cohort found a cumulative long-COVID incidence of under 3% in the current context of mild Omicron reinfections — likely closer to the real-world experience for many healthy working-age adults. This is a context-specific figure from a specific cohort, not a general population prevalence estimate.

Can boosters reduce that risk? A 2025 Canadian study in Clinical Infectious Diseases found substantial protection against long-COVID when vaccination was recent, with attenuation over time. Hybrid immunity — prior Omicron infection plus vaccination — was associated with effectiveness above 85% against long-COVID during reinfection in that cohort, largely regardless of the number of vaccine doses received.

In the large US reinfection cohort, people vaccinated between their first infection and a subsequent reinfection faced lower long-COVID risk than those vaccinated only before their first infection. This was not consistent across all subgroups, but the direction is important: a recent booster tops up immunity that wanes over time.

Is there evidence on the benefits and risks of repeated boosters?

A study of KP.2-targeting vaccines (Ioannou et al., Nature Communications, 2026 — predominantly older adults, mean age 70.7 years, 91% male) found vaccine effectiveness against laboratory-confirmed infection of only 16.6% over a mean follow-up of 172 days. This is the most important corrective to overclaiming: these vaccines are now tools for personal risk attenuation against severe illness, not reliable barriers to infection.

A 2025 NEJM systematic review summarised studies reporting substantial protection against hospitalisation — around 60–70% in some analyses — consistent with strong but time-limited protection against the worst outcomes.

On safety: transient systemic reactions (fatigue, fever, headache) are common. Myocarditis risk is concentrated in younger males and is very rare above age 40. There is no established signal of chronic harm from repeated boosting in the general adult population.

A 2025 NEJM perspective argued there is genuine equipoise about annual boosters for adults aged 50–64, calling this the ideal population for future randomised trials. Several other high-income countries have generally tended to take a narrower, more risk-targeted approach than the US throughout this period. Whether repeated boosting in healthy middle-aged adults confers net benefit beyond robust hybrid immunity remains genuinely unsettled.

What do different public health authorities recommend?

Where everyone agrees: Additional updated doses for adults ≥65 and those with immunocompromising conditions, major cardiometabolic disease, chronic respiratory disease, obesity, or disability. Variant-matched seasonal boosting is standard for these groups across virtually all high-income countries.

Where they diverge: The US historically took the most expansive approach — annual boosters for everyone over 6 months. Even that shifted toward individual decision-making for healthy younger adults in the 2024–25 season. Several other high-income countries have generally tended to take a narrower, more risk-targeted approach throughout.

The key practical divergence comes down to timing and trigger: most countries now favour opportunistic boosting — ahead of winter, before travel, before a high-risk exposure — rather than a fixed annual calendar for lower-risk adults. That is consistent with what the waning immunity data actually supports.

Is funded access to COVID vaccines likely to change?

In New Zealand, COVID-19 vaccines are being progressively integrated into routine immunisation structures. For high-risk groups, funded access is expected to continue. For healthy adults under 65, the direction of travel is toward individual decision-making — consistent with the evidence, which shows modest rather than dramatic absolute benefit for this group.

Expert concerns centre on three things: reduced programme visibility risking uptake erosion even among those who would benefit most; supply chain and regulatory capacity needing to be maintained for rapid response to a more pathogenic variant; and equity of access for Māori and Pacific communities, who carry higher burdens of conditions that elevate COVID-19 risk and must not be left behind as programmes narrow.

What’s the bottom line for healthy adults under 65?

Most healthy adults under 65 in NZ now carry substantial hybrid immunity from vaccination plus prior infection(s). Against that backdrop, hybrid immunity confers effectiveness above 85% against long-COVID during reinfection in cohort studies — largely regardless of how many doses you’ve had. That’s the reassuring part.

The less reassuring part: reinfection risk is ongoing, each infection adds incremental long-COVID risk, and that protection wanes. The case for staying up to date is not “you’ll end up in hospital” — it’s:

That framing — less about hospitalisation, more about long-COVID after the next infection you’re probably going to get — is both scientifically accurate and practically useful.

Does it matter which COVID vaccine you get?

The mRNA platform on which Comirnaty is based has by far the largest real-world evidence base globally. A 2025 NEJM systematic review found that studies restricted to mRNA vaccine recipients generally showed higher effectiveness estimates than studies combining multiple platform types. The relevant question for NZ patients is not which vaccine — it’s when.

Does timing matter — is there a best time to get vaccinated?

The waning problem. Protection peaks around four weeks post-vaccination — roughly 40–50% against infection, around 58% against hospitalisation or death — and declines substantially over the following months. Vaccinating in early March and hoping it holds until July is not the optimal strategy. This is practical risk-based advice, not a formally trialled seasonal rule.

Co-administration with flu and RSV vaccines. There are no anticipated safety concerns with co-administering COVID-19 and influenza vaccines — the NZ Immunisation Handbook explicitly confirms this. Getting both at one appointment is practical and evidence-consistent. No minimum waiting period applies if you prefer separate visits.

Are COVID vaccines safe in pregnancy and breastfeeding?

Pregnancy is itself a risk factor for more severe COVID-19. A Nature Communications systematic review and meta-analysis of 23 studies including over 117,000 vaccinated pregnant people found no evidence of increased risk of miscarriage, preterm birth, placental abruption, pulmonary embolism, postpartum haemorrhage, or reduced birthweight. The same review found the risk of stillbirth was significantly lower in the vaccinated group.

A broader meta-analysis of 71 studies involving over 17 million pregnant persons found no association between COVID vaccination and adverse pregnancy outcomes, regardless of vaccine type or trimester of vaccination — including first trimester.

Vaccination in pregnancy also conveys some passive immunity to newborns via placental transfer of antibodies. There is no evidence of harm from COVID vaccination while breastfeeding.

Should people get COVID, flu, and RSV vaccines — and does the order matter?

Influenza vaccine. Annual vaccination is recommended for all adults. A 2025 NEJM systematic review found pooled influenza vaccine effectiveness of 48% against hospitalisation in adults aged 18–64 — broadly comparable with COVID vaccine effectiveness against the same outcome.

There is no required order between vaccines and no minimum waiting period if given at separate visits. Getting COVID and flu at one appointment removes a meaningful barrier to uptake and is safe.

What is long COVID, how common is it, and who is most at risk?

Long COVID (post-COVID condition or PASC) is defined by WHO as symptoms persisting or arising 3 months or more after SARS-CoV-2 infection, lasting at least 2 months, not explained by an alternative diagnosis. Common symptoms include fatigue, cognitive impairment (brain fog), post-exertional malaise, breathlessness, palpitations, and altered smell or taste — symptoms that can persist for months and materially affect quality of life and work capacity.

How common is it now? A Canadian healthcare worker cohort found a cumulative long-COVID incidence of under 3% per infection in the current Omicron context — this is a context-specific figure, not a general population prevalence estimate, but likely closer to the real-world experience for many healthy working-age adults than the higher figures from earlier waves. A 2025 Nature Communications systematic review and meta-analysis of 50 studies totalling nearly 15 million people confirmed that SARS-CoV-2 infection significantly increases the risk of a wide range of symptoms compared with uninfected controls, with the highest relative risks for loss of smell (RR 4.31) and loss of taste (RR 3.71).

Who is most at risk? Women, those with more severe acute illness, those with pre-existing symptom burden, and those with certain comorbidities (autoimmune conditions, obesity, diabetes). Being under 65 and previously healthy does not confer immunity from long COVID.

Has risk declined? Yes, substantially — from approximately 35% in 2020–21 to around 23% in 2023–24 in one four-year cohort study, reflecting less pathogenic Omicron variants, greater background immunity, and better acute illness management. But 3% of a population getting reinfected repeatedly is not negligible at a societal level.

What vaccine safety signals should people know about?

Myocarditis/pericarditis. The best-established rare adverse event following mRNA vaccination. The incidence is highest in adolescent and young adult males — rates of tens of cases per million doses in males aged 12–39, substantially lower in adults ≥40 — and typically mild and self-resolving. A 2025 NEJM systematic review confirmed this established profile and found no new or amplified myocarditis signal with updated vaccine formulations.

Guillain-Barré syndrome (GBS). A small excess risk was identified with adenoviral-vector vaccines (no longer used in NZ). For RSV vaccines, an estimated 11 excess GBS cases per million doses have been identified — relevant context as RSV and COVID vaccination increasingly occur in the same clinical encounters. No comparable established GBS signal has been confirmed for current mRNA COVID formulations.

Longer-term safety. No credible signal of cumulative harm from repeated boosters has emerged from any large surveillance system. Claims about autoimmune disease, fertility, or long-term neurological harm from mRNA vaccines have been extensively investigated and not substantiated.