In vitro neutralizing activity of BNT162b2 mRNA-induced antibodies
against full B.1.351 SARS-CoV-2 variant
Background: SARS-CoV-2 variation represents a serious challenge
to current COVID-19 vaccines. Recent reports suggest that B.1.351 and
other variants may escape the neutralization activity of the antibodies
generated by current vaccines. Methods: Ninety-nine healthcare
workers undertaking BNT162b2 mRNA vaccination were sampled at baseline,
on the day of the second dose, and 14 days after the latter.
Neutralization activity against SARS-CoV-2 B.1, B.1.1.7 and B.1.351 was
investigated using a Vero-E6 model. Results: Eleven of the
study participants had prior infection with SARS-CoV-2. Neutralization
titers against the B.1 and the B.1.1.7 variants were not statistically
different and were significantly higher than titers against the B.1.351
variant across pre-exposed and non-pre-exposed vaccinated individuals (
p<0.01). While all vaccinated individuals presented
neutralizing antibodies against B.1 and B 1.1.7 after the second dose,
14% were negative against B.1.351, and 76% had low titers (1/20-1/80).
Pre-exposed vaccinated individuals showed higher titers than
non-pre-exposed after the first (median titers of 1/387 versus 1/28,
respectively) and the second doses (1/995 versus 1/703, respectively).
As high as 72% of the pre-exposed vaccinees presented titers
>1/80 after a single dose, while only 11% of non-exposed
vaccinated individuals had titers >1/80.
Conclusions: BNT162b2 mRNA-induced antibodies show a lower in
vitro neutralizing activity against B.1.351 variant compared to
neutralization against B.1.1.7 or B.1 variants. Interestingly, for
individuals pre-exposed to SARS-CoV-2, one dose of BNT162b2 mRNA may be
adequate to produce neutralizing antibodies against B.1.1.7 and B.1,
while two doses of BNT162b2 mRNA provide optimal neutralizing antibody
response against B.1.351 too.