The effect of pre-existing coronavirus antibodies on SARS-CoV-2 infection outcomes in exposed household members

Background/Rationale We investigated the effect of pre-existing antibodies against SARS-CoV-2 and seasonal human coronaviruses on infection outcomes in Omicron BA1/2 exposed household members from January to March 2022. Methods Data from a prospective household study in the Netherlands were used including 63 households with 195 household members exposed to a SARS-CoV-2 Omicron BA1/2 index case. The protocol included repeated nose-throat swab and saliva RT-PCR testing, paired serology, and self-reported daily symptom scoring by household members. Infection outcomes included the occurrence of secondary infections, symptom burden, and CT-value trajectories. We studied the effect of baseline binding antibody levels for SARS-CoVs and seasonal coronaviruses (hCoV) NL63, 229E, HKU1 and OC43 spike protein, on SARS-CoV-2 infection outcomes. Results 132 of 195 (68%) exposed household members developed a SARS-CoV-2 infection. Among exposed household members, higher levels of SARS-CoV-2 at baseline were associated with a reduced risk of secondary infection (adjusted Odds ratio 0.73; 95% Confidence interval 0.55-0.99). No significant differences between antibody levels and symptom burden or CT-value trajectories were observed. Conclusions Our study suggests that prior SARS-CoV-2 antibodies provide some protection against Omicron BA.1/BA.2 infection, while effects on symptom burden or CT-value could not be demonstrated. The results highlight the relatively limited, but not negligible role of cross-protective antibodies, especially when facing immune escape variants of SARS-CoV-2.