Risk of reinfection and disease after SARS‐CoV‐2 primary infection: Meta‐analysis

Abstract

Introduction A precise estimate of the frequency and severity of SARS‐CoV‐2 reinfections would be critical to optimize restriction and vaccination policies for the hundreds of millions previously infected subjects. We performed a meta‐analysis to evaluate the risk of reinfection and COVID‐19 following primary infection. Methods We searched MedLine, Scopus and preprint repositories for cohort studies evaluating the onset of new infections among baseline SARS‐CoV‐2‐positive subjects. Random‐effect meta‐analyses of proportions were stratified by gender, exposure risk, vaccination status, viral strain, time between episodes, and reinfection definition. Results Ninety‐one studies, enrolling 15,034,624 subjects, were included. Overall, 158,478 reinfections were recorded, corresponding to a pooled rate of 0.97% (95% CI: 0.71%–1.27%), with no substantial differences by definition criteria, exposure risk or gender. Reinfection rates were still 0.66% after ≥12 months from first infection, and the risk was substantially lower among vaccinated subjects (0.32% vs. 0.74% for unvaccinated individuals). During the first 3 months of Omicron wave, the reinfection rates reached 3.31%. Overall rates of severe/lethal COVID‐19 were very low (2–7 per 10,000 subjects according to definition criteria) and were not affected by strain predominance. Conclusions A strong natural immunity follows the primary infection and may last for more than one year, suggesting that the risk and health care needs of recovered subjects might be limited. Although the reinfection rates considerably increased during the Omicron wave, the risk of a secondary severe or lethal disease remained very low. The risk–benefit profile of multiple vaccine doses for this subset of population needs to be carefully evaluated.

Older age and depressive state are risk factors for re-positivity with SARS-CoV-2 Omicron variant

“…And because after the outbreak the whole county was centralized controlled and all infected patients were isolated, thus we assumed that BA2.2 was the predominant version circulating in this region at this time. The re-positivity rate with Omicron BA.2.2 reached 16.4%, which is higher than that in a previous report ( 25 ). In addition, one study reported that reinfection was found in 26 (0.46%) of 5,554 alpha, 209 (1.16%) of 17,941 delta, and 520 (13.0%) of 3,992 Omicron variants ( 26 ).…”

COVID-19 vaccines reduce the risk of SARS-CoV-2 reinfection and hospitalization: Meta-analysis

“…Vaccinated subjects were defined as those receiving ≥ 1 dose of the COVID-19 vaccines currently approved ≥ 14 days before the reinfection. The following search strategy was adopted, without language restrictions: (coronavirus * or coronovirus * or coronavirinae * or Coronavirus * or Coronovirus * or Wuhan * or Hubei * or Huanan or "2019-nCoV" or 2019nCoV or nCoV2019 or "nCoV-2019" or "COVID-19" or COVID19 or "WN-CoV" or WNCoV or "HCoV-19" or HCoV19 or CoV or "2019 novel * " or Ncov or "n-cov" or "SARS-CoV-2" or "SARSCoV-2" or "SARSCoV2" or "SARS-CoV2" or SARSCov19 or "SARS-Cov19" or "SARSCov-19" or "SARS-Cov-19" or Ncovor or Ncorona * or Ncorono * or NcovWuhan * or NcovHubei * or NcovChina * or NcovChinese * ) AND (reinfection * or reinfection * or second episode or recurrence * or recrudescence * or relapse * or RCOVID19) (2). The reference lists of reviews and retrieved articles was also screened, for additional pertinent papers (11).…”

“…Clarifying the frequency and predictors of SARS-CoV-2 reinfections is crucial to determine the course of the pandemic, and to optimize restriction and vaccination policies (1)(2)(3). Solid evidence is currently available on the frequency of reinfections after the emergence of the Omicron variant: a recent proportion meta-analysis including 15 million subjects recovered from a first infection estimated an overall reinfection rate of 3.3% in the first 3 months of Omicron predominance, likely increasing (2). However, the potential addictive protection conferred by hybrid immunity, generated by the combination of prior infection and vaccination, as compared to the sole natural immunity, remains to be fully disclosed (4,5).…”

“…A few population-based studies suggested that reinfection is less likely in vaccinated vs. unvaccinated subjects, but the magnitude of the association varied across studies, which differed for patients' characteristics, exposure risk, type of SARS-CoV-2 vaccine received, definition of reinfection adopted, and extent of measured confounding (4,(6)(7)(8). In a recent meta-analysis, the overall reinfection rate among vaccinated subjects was quantified to be as low as 0.32%, as compared to 0.74% among previously infected, unvaccinated individuals, but these estimates were obtained from raw, unadjusted data (2). Additionally, only limited data are available on the time course of natural and hybrid immunity (9), and the extent of its waning, particularly due to Omicron infections, is not yet well characterized (4,9).…”

SARS-CoV-2 Omicron Variant of Concern: Everything You Wanted to Know about Omicron but Were Afraid to Ask

“…During the first 3 months of the omicron wave, the reinfection rate was 3.31% [95% confidence interval (CI): 1.15–6.53] compared to 0.57% (95% CI: 0.28–0.94) on the alpha wave and 1.25% (95% CI: 0.97–1.55) on the delta wave. 29 These results showed that the pre-existing immunity from prior infection might have less protective effect on the omicron variant.…”