Reinfection rates, change in antibody titers and adverse events after COVID-19 vaccination among patients previously infected with COVID-19 in Metro Manila, Philippines: a secondary analysis of a completed cohort study

Abstract

Background Variation in immune response to COVID-19 vaccines is observed among different ethnicities. We aimed to describe the reinfection rates, change in antibody titers, and adverse events among Filipinos. Methods This is a secondary analysis of a cohort study of 307 participants within one year of having COVID-19 infection. We measured COVID-19 antibody levels at pre-determined timepoints (Days 21, 90, 180, 270, and 360 from initial infection). We monitored for COVID-19 symptoms and obtained details on COVID-19 vaccination. An adjudication committee classified the participants as probable, possible, or unlikely COVID-19 reinfection. We determined the probable reinfection rate, adverse events, and the geometric mean titer (GMT) ratio of pre- and post-vaccination antibody levels according to type and brand of COVID-19 vaccine. Results At the end of the follow-up period, 287 (93.5%) out of 307 study participants were fully vaccinated, 1 was partially vaccinated (0.3%), and 19 were unvaccinated (6.2%). Among the fully vaccinated participants, those given mRNA vaccines had the lowest reinfection rate (19.2 cases/100 person-years, 95% CI 9.6, 38.4), followed by viral vector vaccines (29.8 cases/100 person-years, 95% CI 16.9, 52.4). We observed the highest reinfection rate among those given inactivated virus vaccines (32.7 cases/100 person-years, 95% CI 23.6, 45.3). The reinfection rate was 8.6 cases/100 person-years (95% CI 4.1, 17.9) for unvaccinated participants and 3.6 cases/100 person-years (95% CI 0.5, 25.3) for partially vaccinated participants. We observed the largest rise in antibody titers among those given mRNA vaccines (GMT ratio 288.5), and the smallest rise among those given inactivated virus vaccines (GMT ratio 16.7). We observed the highest percentage of adverse events following immunization with viral vector vaccines (63.8%), followed by mRNA vaccines (62.7%), and the lowest for inactivated virus vaccines (34.7%). No serious adverse events were reported. Conclusion Vaccinees given the mRNA vaccines had the lowest reinfection rate and the highest rise in antibody titers. Vaccinees given inactivated virus vaccines had the highest reinfection rate, smallest rise in antibody titers, and lowest percentage of adverse events. The small sample size and imbalanced distribution of the type of vaccines received limits the external generalizability of our results. Study Registration The cohort study was registered at the Philippine Health Research Registry on December 14, 2020 (PHRR201214-003199).

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“…Our results also suggested no significant difference found in reinfection rates between the CoronaVac vaccine and the BNT162b2 vaccine. However, a previous study has reported that receiving mRNA vaccines leads to a lower reinfection rate than inactivated vaccines [34],…”

“…Our results also suggested no significant difference found in reinfection rates between the CoronaVac vaccine and the BNT162b2 vaccine. However, a previous study has reported that receiving mRNA vaccines leads to a lower reinfection rate than inactivated vaccines [34], while another study suggested that Combined vaccination may offer superior reinfection protection than either alone [35]. Considering the potential long-term persistence of the SARS-CoV-2 virus, individuals with relatively lower immune responses may benefit from a booster vaccination after primary infection, and further investigations were required to confirm the effects of different vaccine types.…”

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“…As COVID-19 becomes endemic globally and immunization protocols evolve, people experiencing numerous successive natural and/or artificial SARS-CoV-2 exposures, may undergo more extreme immune PLOS ONE responses. In response to the rapid increase in reported levels of anti-SARS-CoV-2 antibody titers, some laboratory protocols now report results up to 250,000 U/mL [16]. While a clinical antibody-based threshold of protection against COVID-19 infection has not yet been defined, serological results remain important in clinical decision-making, such as vaccination protocols for immunosuppressed patients.…”