Short Communication
Single-dose BNT162b2 mRNA COVID-19 vaccine significantly boosts neutralizing antibody response in health care workers recovering from asymptomatic or mild natural SARS-CoV-2 infection

https://doi.org/10.1016/j.ijid.2021.05.033Get rights and content
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Highlights

  • SARS-CoV-2 neutralizing antibody (NtAb) titres in health care workers (HCWs).

  • After 313 days from a mild, asymptomatic infection NtAbs are often still detectable.

  • One vaccination dose strongly boosts NtAb titers in previously infected HCWs.

  • One dose boosts NtAbs in previously infected more than two doses in uninfected HCWs.

  • Second dose significantly boosts NtAbs elicited by first dose in uninfected HCWs.

Abstract

Objectives

To measure SARS-CoV-2 neutralizing antibody (NtAb) titres in previously infected or uninfected health care workers who received one or two doses of BNT162b2 mRNA COVID-19 vaccine.

Methods

NtAbs were titrated as dose-inhibiting 50% virus replication (ID50) by live virus microneutralization. We evaluated 41 health care workers recovering from mild or asymptomatic infection at first vaccination dose (T1_inf) and 21 days later (T2_inf). Sixteen uninfected health care workers were evaluated 20 days after first dose (T2_uninf) and 20 days after second vaccine dose (T3_uninf).

Results

At T2_inf, but not at T1_inf, there was a significant correlation between days from diagnosis (median 313, interquartile range 285–322) and NtAb levels (P = 0.011). NtAb titres increased at T2_inf with respect to T1_inf (1544 (732–2232) vs 26 (10–88), P < 0.001). Similarly, there was a significant increase in NtAb titres at T3_uninf compared with T2_uninf (183 (111–301) vs 5 (5–15), P < 0001). However, NtAb levels at T2_inf were significantly higher than those at T2_uninf and T3_uninf (P < 0.0001 for both analyses).

Conclusions

A single vaccination in people with mild or asymptomatic previous infection further boosts SARS-CoV-2 humoral immunity to levels higher than those obtained by complete two-vaccination in uninfected subjects.

Keywords

Health care workers
BNT162b2 mRNA COVID-19 vaccine
Neutralizing antibody response

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