High transmission changes the antibody level associated with protection
A single peer-reviewed study of 1828 symptomatic people in the Dominican Republic found that antibody levels associated with protection varied with community transmission. The antibody gap between infected and uninfected participants narrowed during high transmission. Simulations reproduced the shift through repeated exposure, highlighting a limit on applying one antibody threshold across different settings.
Science··Midday
Protection depends on exposure
Researchers in the Dominican Republic observed a changing relationship between antibody levels and infection risk as community transmission rose. This was a single peer-reviewed observational study. Eric J. Nilles and colleagues analyzed 1828 people who sought care for fever or other symptoms at two surveillance sites. The finding concerns the relationship between immunity and repeated exposure, with consequences for comparing antibody-based protection across communities.[1]
The gap narrowed during high transmission
The investigators classified periods using the share of positive polymerase chain reaction (PCR) tests. Below 15 per cent counted as low transmission; at least 15 per cent counted as high. Uninfected participants had geometric mean antibody titers 14.7 times those of infected participants during low transmission, but this ratio fell to 2.5 during high transmission. The models also included variant period and age, alongside vaccine history and the interval since vaccination.[1]
Repeated contact reproduced the shift
Simulations reproduced the shifted protection curves through repeated infectious contacts even when susceptibility during each exposure stayed constant. Actual contact counts were not measured, however: test positivity represented community transmission. Antibodies were measured when participants enrolled, which may differ from their levels at exposure. The sample covered symptomatic healthcare seekers, so the results do not establish one universal antibody threshold for the whole population or for severe disease.[1]
