Effect of previous SARS-CoV-2 infection and vaccination on Omicron infection

In a recent study posted on medrex sib*In a preprint server, researchers investigated previous severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the effects of vaccination on SARS-CoV-2 Omicron infection.

Background

Prior infection with coronavirus disease 2019 (COVID-19) by vaccination confers hybrid immunity and reduces the risk of SARS-CoV-2 Omicron infection compared to vaccination alone.Increased use of self-administration antigen Testing, as well as untested disease, may influence the results of these case-control studies. still unknown.

About research

In the current study, researchers determined the protective efficacy of past infections and vaccines against infection with SARS-CoV-2 Omicron.

From May 2021 to December 2021, we recruited participants for Vaccine Research COVID-19 (VASCO) using random emails and campaigns on social media. Adults aged 18 to 85 years living in the community were included, and adults aged 60 to 85 were oversampled. At baseline, the participant completed questionnaires regarding demographics, COVID-19 vaccination, his previous SARS-CoV-2 infection, and comorbidities.

Monthly follow-up included questions about COVID-19 vaccination, COVID-19-like symptoms, and testing methods. After the first year of participation, follow-up surveys were collected quarterly instead of monthly. Participants are also required to report each COVID-19 vaccination and all positive SARS-CoV-2 tests using an online application so that data can be collected in real time.

Participants were requested to self-collect finger prick samples for serum analysis at baseline and every 6 months during follow-up. were invited to provide fingertip samples one month after their first vaccination schedule. Participants with COVID-19-like symptoms or who had close contact with an individual infected with SARS-CoV-2 were offered a self-administered antigen test.

Study results included SARS-CoV2 infections throughout the study period. COVID-19 infection was determined by any self-reported positive SARS-CoV-2 test and either detection or a 4-fold increase in SARS-CoV-2 nuclear protein (N) antibodies.

result

Between 10 January 2022 and 1 September 2022, a total of 43,257 people contributed 8,291,966 person-days and 20,418 SARS-CoV-2 infection cases. Nearly 11% of these infections were diagnosed solely by N antibodies, the remainder reported according to SARS-CoV-2 positive (self) testing. Also, of the 9,727 infections that occurred before the study period, 12.9% were detected by his N antibody alone, and the rest were diagnosed by positive (self)testing.

Hybrid immunization was associated with greater SARS-CoV-2 Omicron infection than vaccine-induced immunity up to 30 weeks after the last immunization event in all three cohorts, including individuals with 2, 3, or 4 prior immunization events. ensured greater protection against A 71% to 85% reduction in hazard rate compared to vaccine-induced immunity was observed 4-10 weeks after the last immunization event.

Comparisons with infection-induced immunity can be made in persons with two previous immunizations. During the study period, it was very rare for the subject to have had more than one infection and not to have been vaccinated.In the stratum of her two previous vaccination events, infection-induced immunity was higher than hybrid immunity. also provided a lot of protection. However, this difference did not show statistical significance.

Compared to vaccine-induced immunity, protection against SARS-CoV-2 infection decreased significantly and rapidly over time since the previous incident of hybrid immunity. For example, in strata with three previous vaccination episodes, hybrid and vaccine-induced immunity to SARS-CoV-2 infection was nearly 80% after 30–40 weeks compared to 4–10 weeks after the last event. and decreased by 33%.

Hybrid immunization continued to provide better protection against infection until it approached vaccination-induced immunity levels at 30–40 weeks. Furthermore, the geometric mean concentration (GMC) associated with hybrid immunization was lower than that of vaccine-induced immunity after 20–30 weeks.

Similar rates of loss of SARS-CoV-2 spike (S) antibodies were observed with vaccine-only and hybrid immunizations. Notably, in strata with 3 previous immunization episodes, the reduction in S antibody concentrations was 64% between weeks 30 to 40 and weeks 4 to 10 of hybrid and vaccine-induced immunization. Moreover, GMC values ​​were significantly lower with challenge than with hybrid or vaccine, even though challenge was highly efficient. However, these estimates are based on small sample sizes and are therefore uncertain.

Regardless of the number or type of vaccination episodes, S antibody levels correlated in a dose-response trend with the risk of developing infection 3 weeks after receipt of serological samples. This was notable because a 71% lower incidence of infection was observed in those with the highest S antibody concentrations compared to those with the lowest S antibody concentrations.

Conclusion

The results of this study concluded that hybrid immunization provides superior protection against SARS-CoV-2 Omicron infection compared to vaccine-induced immunity. This effect appears independent of the order and quantity of immune events. However, having many infections and vaccinations when a person is not particularly susceptible may protect against devastating consequences during times of greater vulnerability or when new subspecies are introduced.

*Important Notices

medRxiv publishes non-peer-reviewed, preliminary scientific reports and should not be considered conclusive, to guide clinical practice/health-related actions, or to be treated as established information .