Standard dosing intervals for BNT162b2 and mRNA-1273 SARS-CoV-2 vaccines are 21 and 28 days, respectively. 1 Data suggest improved effectiveness of ChAdOx1 adenoviral 2 and other nonreplicating vaccines 3 with increased dosing intervals, but little data exist for mRNA vaccines. This study investigated the immunogenicity of extended mRNA vaccine dosing intervals.

Health jurisdictions have seen a near-disappearance of Respiratory Syncytial Virus (RSV) during the first year of the COVID-19 pandemic. Over a corresponding period, we report a reduction in RSV antibody levels and neutralization in women and infants one year into the COVID-19 pandemic (February – June 2021) compared to earlier in the pandemic (May – June 2020), in British Columbia (BC), Canada. This supports that humoral immunity against RSV is relatively short-lived and its establishment in infants requires repeated viral exposure. Waned immunity in young children may explain the inter-seasonal resurgence of RSV cases in BC as seen also in other countries.

Live viral neutralizing antibody titers are an accepted measure of immunity; however, testing procedures are labor-intensive. COVID-19 antibody and angiotensin converting enzyme-2 (ACE-2) levels have been used as surrogates to live viral neutralizing antibody titers; however, validity among vaccinated individuals is unclear.

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