SARS-CoV-2 reinfection during the omicron wave was found to be more common among individuals in Iceland who received 2 or more vs 1 or fewer COVID-19 vaccine doses, according to a report published in JAMA Network Open.

In this population-based cohort study, conducted between December 2021 and February 2022, researchers assessed the rate of COVID-19 reinfection during the omicron wave among 11,536 individuals in Iceland.

Eligible participants included those with a polymerase chain reaction (PCR)-confirmed SARS-CoV-2 reinfection, which the researchers defined as PCR-confirmed infection 60 days or more following a previous positive result. Logistic regression was used to estimate rate of SARS-CoV-2 reinfection on the basis of patient age, vaccination status, and the number of days between initial infection and reinfection.

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The median patient age was 31 (range, 0-102) years, 51% were men, 25.5% had received at least 1 vaccine dose, and the median time between initial infection and reinfection was 227 days (range, 60-642).

A total of 1327 (11.5%) participants were reinfected with SARS-CoV-2 within the study period. The rate of reinfection was increased among participants who had previously received 1 or fewer (n=8598) vs 2 or more (n=2938) doses of a COVID-19 vaccine (11.7% vs 10.9%). Stratified by age, the highest rate of reinfection was observed among participants between 18 and 29 years of age vs those 75 years of age and older (15.1% vs 4.1%).

Further analysis was performed after the logistic regression model was adjusted to a reference individual aged 18 to 29 years who received 1 or fewer vaccine doses and was initially infected 227 days before study enrollment. Results showed there was an increased risk for reinfection 18 months after initial infection compared with 3 months after initial infection (adjusted odds ratio [aOR], 1.56; 95% CI, 1.18-2.08), indicating the probability of reinfection increased over time. In addition, receipt of 2 or more vaccine doses was associated with an increased risk for reinfection compared with 1 or fewer doses (aOR, 1.42; 95% CI, 1.13-1.78).

Limitations of this study include the inability to adjust for potential confounders related to prior SARS-CoV-2 infection, vaccine eligibility, and underlying medical conditions. Of note, 71.1% of individuals in Iceland had received at least 1 COVID-19 vaccine dose at the time of study enrollment, compared with 25.5% of participants included in this analysis.

According to the researchers, “[these] results suggest the reinfection is more common than previously thought.”


Eythorsson E, Runolfsdottir HL, Ingvarsson RF, Sigurdsson MI, Palsson R. Rate of SARS-CoV-2 reinfection during an omicron wave in Iceland. JAMA Netw Open. Published online August 3, 2022. doi:10.1001/jamanetworkopen.2022.25320

This article originally appeared on Infectious Disease Advisor