A preprint, an unpublished non-peer reviewed study, looks at the T-cell and antibody respondes to the first dose of Pfizer-BioNTech COVID-19 vaccine in previously infected and infection-naïve UK healthcare workers.
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This large, well-controlled study of UK health care workers demonstrates that a single dose of the Pfizer BioNtech COVID-19 vaccine induces antibody and T cell responses comparable to those seen after natural infection. As natural infection has been shown to confer greater than 80% protection against reinfection, these data offer considerable reassurance that JCVI’s somewhat controversial decision to recommend a 12 week interval between COVID-19 vaccine doses is a safe, effective and pragmatic approach to maximising public health given current constraints.
Importantly, this study shows that vaccination of previously infected individuals not only boosts their immune responses but also broadens the repertoire of immune responses to SARS-CoV-2 and, in so doing, enhances the response to several variants of concern including the so-called Kent, South African and Brazilian variants. These data demonstrate the importance of vaccinating everyone, including people who have already been infected.
A single dose of vaccine in uninfected individuals also induces neutralising antibodies to the variants of concern, although at much lower levels. It remains to be seen whether these antibodies can be enhanced after a second dose of the current vaccine or whether a further boost – possibly with a second generation, variant-specific vaccine – might be needed.
This interesting study adds to the existing body of work from antibody studies, now showing that both antibodies and also T cell responses show a considerable boost in people who have had their first dose of Pfizer vaccine, having been previously primed through natural infection with the virus. Responses are extremely high – higher than seen for the conventional situation of two vaccine doses without prior infection. Of course, findings such as this have inevitably led to debate about whether vaccine supplies could be stretched further by offering only a single dose to those known to have been previously infected. For most of the world, including the UK, there may be sufficient diagnostic uncertainty as to who was definitely infected to make this approach hard to implement efficiently.