Thread by @celinegounder

1/ How is it possible that vaccines could prevent severe disease, hospitalizations, & deaths from COVID

BUT not prevent mild infections & onward transmission?

advances.sciencemag.org/content/7/12/e…

2/ If the vaccines induce systemic immunity protecting the lungs

but not mucosal immunity in the upper airway (nose, throat),

you could still get upper airway SARS-CoV-2 infection, causing no or mild symptoms

without severe illness (e.g. hypoxia or low oxygen levels).

3/ We're already seeing the benefit of mixing-matching different types of vaccines (what we call heterologous prime-boost).

Perhaps we should be doing the same with injectable COVID vaccines and intranasal COVID vaccines.

4/ Intranasal vaccines show promise in eliciting mucosal IgA antibodies.

science.sciencemag.org/content/373/65…