Effectiveness and duration of additional immune defense provided by SARS-CoV-2 infection before and after receiving the mRNA COVID-19 vaccine BNT162b2

Abstract

Background

Our investigation focused whether infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) before or after receiving the mRNA COVID-19 vaccine can increase immune protection. And we also investigated relationship of infection acquired.

Methods

Three shots of the mRNA coronavirus disease 2019 (COVID-19) vaccine BNT162b2 were administered to 736 healthcare workers at Tokyo Shinagawa Hospital. Serum samples were collected before the first shot (P1), at one month (P2), and at six months (P3) after the second shot and at one month after the third shot (P4). The presence of infection was assessed using IgG against the nucleocapsid (IgG (N) and RBD in the spike protein of SARS-CoV-2. We defined infection before P2 as natural infection (NI) and infection between P2 and P3 as breakthrough infection (BI) and compared susceptibility to further infection between the NI (−) and NI (+) groups and between BI (−) and BI (+) groups. Events in 485 participants who had a complete dataset of IgG (N) and IgG (RBD) from P1 to P4 were analyzed.

Results

The presence of SARS-CoV-2 infection before P2 were examined by examining the titers of IgG (N)P1, IgG (N) P2, and IgG (RBD) P1 that exceeded the cutoff values. Consequently, 35 participants (7.22 %) were categorized into the NI (+) group, whereas 450 (92.8 %) were categorized into the NI (−) group. Between P2 and P3, the NI (−) group showed a higher rate of SARS-CoV-2 infection than the NI (+) group; however, there was no significant difference in the infection rate between P3 and P4. The infection rate was significantly lower in the BI (+) group than in the BI (−) group. Pre-primary vaccination infection significantly increased IgG (RBD) levels between P1 and P3. Post-primary vaccination infection significantly increased IgG (RBD) levels between P3 and P4.

Conclusions

Infection with SARS-CoV-2 before or after receiving the mRNA COVID-19 vaccine can increase immune protection; however, the duration of this effect may be limited.