Waning of post-vaccination neutralizing antibody responses against SARS-CoV-2, a systematic literature review and meta-analysis

Background Mass COVID-19 vaccination and the continuous introduction of new viral variants of SARS-CoV-2, especially of Omicron subvariants, has resulted in an increase in the proportion of the population with hybrid immunity at various stages of waning protection. We systematically reviewed waning of post-vaccination neutralizing antibody titers in different immunological settings to investigate potential differences. Methods We searched for studies providing data for post-vaccination neutralizing antibody responses against SARS-CoV-2 in PubMed, bioRxiv, and medRxiv from Dec 15, 2021, to Jan 31, 2023, using keywords related to COVID-19, vaccination, and antibody neutralization. We used random effects meta-regression to estimate the average fold-reduction in post-vaccination neutralizing antibody titers against the Index strain or Omicron BA.1. from month 1 to month 6 post last dose, stratified by vaccination regimen (primary or booster) and infection-naïve vs hybrid-immune status. Findings In total, 26 studies reporting longitudinal post-vaccination neutralizing antibody titers were included. Neutralization titers against the Index variant were available from all studies for infection-naïve participants, and from nine for hybrid-immune participants. Against Omicron BA.1, nine and eight studies were available for infection-naïve and hybrid-immune cohorts, respectively. In infection-naïve cohorts, post-vaccination neutralization titers against the Index strain waned 5.1-fold (95% CI 3.4-7.8) from month 1 to month 6 following primary regimen and 3.8-fold (95% CI 2.4-5.9) following the booster. Titers against Omicron BA.1 waned 5.9-fold (95% CI 3.8-9.0) in infection-naïve, post-booster cohorts. In hybrid-immune, post-primary vaccination cohorts, titers waned 3.7-fold (95% CI 1.7-7.9) against the Index strain and 5.0-fold (95% CI 1.1-21.8) against Omicron BA.1. Interpretation No obvious differences in waning between post-primary or post-boost vaccination were observed for vaccines used widely to date, nor between infection-naïve and hybrid-immune participants. Titers against Omicron BA.1 may wane faster compared to Index titers, which may worsen for more recent Omicron sub-variants and should be monitored. Relatively small datasets limit the precision of our current analysis; further investigation is needed when more data become available. However, based on our current findings, striking differences in waning for the analyzed and future comparisons are unlikely. ### Competing Interest Statement MMH and MDK report research grants from Pfizer (all paid to the institution) for unrelated projects. All other authors declare no competing interests. ### Funding Statement This project was funded by the Coalition for Epidemic Preparedness Innovations, grant number 138587. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors