Vaccinated persons present a higher coronavirus transmission risk than unvaccinated persons starting a few months from vaccination.
corrected
COVID-19 vaccines are injected intramuscularly and produce systemic immunity (Bleier, Ramanathan, and Lane 2021). They do not produce strong or long-lasting mucosal immunity (Tiboni, Casettari, and Illum 2021), which is another part of the natural immune response to infection, even an asymptomatic one. (Russell et al. 2020) provides a mucosal immunity review.
It was known from the start that the current COVID-19 vaccines do not provide sterilizing immunity. Another known fact is that even in vaccinated persons, the coronavirus can infect mucosal surfaces of the upper respiratory tract for at least a short time, where it can grow and be shed before being neutralized by the systemic immunity. It seemed not a major factor at the start of the vaccines roll out. Nevertheless, it was predicted that the rise of vaccine resistant and more infectious variants would create the problem of asymptomatic shedding from vaccinated persons (Goldstein 2021).
This has happened and was confirmed by direct measurements (Chia et al. 2021). This study found that vaccinated persons have the same initial viral load as unvaccinated ones, as tested by nasal swab. In the same group, the vaccinated persons were three times more frequently asymptomatic than unvaccinated ones. When symptomatic, vaccinated persons had fewer symptoms than unvaccinated persons, thus making the disease harder to notice. Continue reading Asymptomatic Spread by Vaccinated Persons →