COVID-19 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 individuals (N=11,536) in Iceland. Eligible participants included those with a polymerase chain reaction (PCR)-confirmed COVID-19 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 COVID-19 reinfection on the basis of patient age, vaccination status, and the number of days between initial infection and reinfection.
Among participants included in the analysis, the median age was 31 (range, 0-102) years. The researchers noted that 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 COVID-19 within the study period. Of note, 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 aged between 18 and 29 years vs those 75 years 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 include the inability to adjust for potential confounders related to prior COVID-19 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