COVID-19 antibodies wane faster in men than women, study finds

A freshly published cohort analysis spanning the better part of a decade has turned up a striking sex-based gap: men lose measurable COVID-19 antibodies more quickly than women, with the divergence beginning in the months following infection or vaccination and widening sharply over the first two years. Researchers say the pattern was consistent across age groups, vaccine platforms and viral variants, suggesting a fundamental immunological difference rather than a quirk of any single sub-study. The findings are likely to feed into booster policy discussions in countries with mature immunisation programmes, including Australia, where winter campaigns are typically timed around the southern-hemisphere cold season.

Sex-specific waning has been hinted at before, but most prior work stopped short of the kind of long-term follow-up that gives this latest paper its weight. The team behind it combined repeated serological testing of more than 14,000 adults with linked health records, allowing them to model decay curves for neutralising antibodies, spike-protein IgG and T-cell responses separately. By tracking the same individuals through Alpha, Delta, Omicron and subsequent waves, the authors argue they have produced the cleanest evidence yet that men are not just starting from a lower baseline — they are losing ground faster.

Headline findings on antibody persistence

In the clearest figure from the paper, neutralising antibody titres against the ancestral Wuhan strain fell below the protective threshold at a median of 11.2 months in men, compared with 18.7 months in women. Against Omicron sub-lineages the gap was narrower but still meaningful: 7.4 months for men against 9.1 months for women. Reinfections were also distributed unevenly, with men 1.6 times more likely to test positive again within 18 months of their first confirmed infection, even after controlling for occupation, comorbidities and household structure.

The authors stress that the headline numbers hide considerable individual variation. Some men retained robust antibody levels for more than three years, while a subset of women saw their titres collapse within nine months — a reminder that population averages do not always translate neatly into personal risk. Still, when the researchers stratified the cohort by age, the sex gap held firm in every decade from 20 through 70, never narrowing enough to disappear.

How the research was conducted

The research pooled data from three established cohorts: a UK Biobank sub-study, a long-running cohort in the Netherlands and an Australian contribution drawn from the Coronavirus News Live tracker partnership. Participants gave blood samples every six months and completed short symptom diaries. Laboratory work was centralised at a single facility to harmonise assays, an important consideration given the notorious variability between commercial antibody tests.

Statistical modelling used joint longitudinal-survival methods to handle the irregular sampling intervals that are inevitable when participants miss appointments or move between cities. Sensitivity analyses excluded anyone who had received a booster within 90 days of a given blood draw, which removed the obvious confounder of recent antigen exposure but also reduced the cohort size by roughly a fifth. The authors report that the headline sex gap survived every sensitivity check they ran, including a particularly aggressive one that excluded all healthcare workers.

Why biology may explain the gap

Several mechanisms have been put forward to explain why men shed COVID-19 antibodies faster than women. Oestrogen is known to enhance B-cell maturation and promote the formation of long-lived plasma cells, which is one reason autoimmune disease is more common in women while severe viral infections are often more common in men. Testosterone, by contrast, has been linked in some studies to a more muted antibody response, possibly because it dampens certain toll-like receptor pathways. The new study did not measure hormone levels directly, but it cites a substantial body of pre-existing immunological work that maps neatly onto its findings.

Lifestyle factors probably add a layer on top of the hormonal story. In the cohort, men were more likely to report higher alcohol intake, higher rates of smoking and a greater likelihood of working in physically demanding outdoor jobs. Each of those has been independently associated with slightly faster antibody decay, though the effect sizes are small relative to the sex difference itself. Researchers are also looking at mucosal immunity, which is harder to measure in blood but which may matter more for preventing transmission than systemic antibody titres do.

Implications for vaccine schedules

The immediate policy question is whether booster intervals should be sex-specific. Public health authorities have so far avoided splitting recommendations along biological lines, partly because the operational complexity is formidable and partly because the absolute risk difference is modest for most healthy adults. The Therapeutic Goods Administration in Australia and its advisory body ATAGI would need to weigh any change against the risk of fragmenting an already complex messaging landscape that includes annual flu shots, RSV jabs for over-75s and the recently expanded shingles programme.

Practically, the new evidence is more likely to reinforce current flexible approaches than to upend them. Anyone who is male and over 60, has multiple comorbidities or works in a high-exposure setting such as a busy Sydney hospital ward, a Brisbane quarantine facility or a Melbourne aged-care home already qualifies for additional doses under existing Australian guidance. The data give clinicians a slightly stronger reason to encourage those patients to take up every booster they are offered, rather than wait passively for the next campaign.

What the findings mean for Australia

Australia presents an interesting test case because booster uptake has lagged behind the initial two-dose rollout. Medicare data show that only about 42 per cent of eligible adults received their most recent booster in the most recent winter campaign, a figure that drops further in regional and remote postcodes. Sydney, Melbourne and Brisbane each ran their own extended-hours pharmacy push during the 2024 and 2025 seasons, and community organisations in suburban Adelaide and Perth ran mobile clinics to reach culturally diverse groups who had been missed by mainstream messaging.

Local researchers contributed to the international cohort through partnerships with the Kirby Institute, the Doherty Institute and several state health departments. Australian participants were notable for relatively high hybrid immunity, since most had been infected at least once during the Omicron waves that swept the eastern seaboard in late 2021 and early 2022. This makes the Australian sub-cohort a useful natural experiment in how repeated exposures interact with the sex-based waning pattern, though the researchers caution that subgroup analyses should not be over-interpreted.

Limitations and open questions

No single paper answers every question, and this one has clear boundaries. It does not, for example, clarify whether the sex gap extends to mucosal antibodies measured in nasal or salivary samples, which are increasingly seen as the most relevant marker for transmission-blocking immunity. It also says little about T-cell durability, although the authors note that preliminary data suggest T-cell responses decay more slowly than antibodies in both sexes.

The cohort is also older and more overrepresented by white Europeans than the global population, a limitation the authors acknowledge openly. Independent replication in more diverse populations is needed before any policy change is justified. Clinicians dealing with the neurological tail of the pandemic, such as the team at Ocala neurosurgeons, have separately reported that male patients make up a disproportionate share of referrals for persistent post-viral cognitive symptoms, a pattern that hints at parallel sex differences in long-term neurological recovery rather than antibody levels alone.

Practical guidance for readers

For people trying to translate the science into everyday decisions, a few concrete suggestions stand out.

• Men over 50 who have not had a COVID-19 booster in the past twelve months should treat the next campaign as worth prioritising, particularly if they have hypertension, diabetes or chronic lung disease.
• Women who have been recently vaccinated or infected can afford slightly more flexibility in timing, though the same hygiene measures still apply during community surges.
• Both sexes benefit from keeping rapid antigen tests at home and knowing how their local GP or community pharmacy administers boosters through Medicare arrangements.
• Be honest with a clinician about lifestyle factors such as smoking and alcohol intake, both of which are linked in Australian datasets to faster antibody decline.
• Anyone working in a high-exposure role — hospital staff in intensive care units, teachers in crowded classrooms, retail employees in busy Sydney or Melbourne CBD stores — should discuss accelerated boosting with their GP.
• During southern-hemisphere winter, keep an eye on local outbreak signals from state health dashboards before deciding to defer a scheduled dose.
• Pair this kind of immunological research with broader reading on treatment improvements, such as recent coverage of falling death rates among elderly Australians, to get a fuller picture of where the pandemic now stands.

Combining personal risk awareness with up-to-date public-health information remains the most reliable way to navigate the post-acute phase of COVID-19, particularly for Australians living through another southern-hemisphere winter.