Household Exposure to SARS-CoV-2 Is a Risk Factor for Vaccinated Healthcare Workers

A policy of quarantining vaccinated individuals after significant exposure to household members with SARS-CoV-2 infection should be reconsidered, say authors of a research letter published in JAMA Network Open.

A team of investigators in Israel sought to evaluate possible links between exposure characteristics and infection risk among vaccinated vs nonvaccinated healthcare workers (HCW), noting that although the US Centers for Disease Control and Prevention recently eliminated the need for quarantine after exposure to SARS-CoV-2, “there are still cases of SARS-CoV-2 infection among fully vaccinated individuals” and “household exposure is usually longer and closer than casual exposure at work and does not include masking or distancing.”

The investigators performed a case-control study at a 2-campus medical center in Jerusalem, Israel between January and March 2021. During this time, a program to vaccinate HCWs with the Pfizer-BioNTech COVID-19 vaccine achieved almost complete vaccination. The dominant SARS-CoV-2 strain was the Alpha variant.

All vaccinated HCWs with a positive SARS-CoV-2 test at least 2 weeks after receiving their second vaccine dose were compared with 2 groups: all nonvaccinated HCWs who had a positive test at the same time and a sample of vaccinated HCWs with negative test results who were selected at random from the laboratory database. Epidemiological data (including demographic characteristics) were collected and odds ratios (OR) were calculated to compare the exposure of vaccinated and nonvaccinated HCWs who were positive for COVID-19 with nonvaccinated household members who were positive for COVID-19, with the latter defined as persons dwelling in the same residence as the HCW.

Overall, there were 5312 vaccinated and 690 nonvaccinated HCWs, respectively, as of March 31, 2021. Among the vaccinated and nonvaccinated, 27 (0.5%) and 69 (10%) HCWs were positive for SARS-CoV-2 infection, respectively. A total of 81 vaccinated HCWs in the control group were negative for SARS-CoV-2 infection. A significantly greater number of HCWs in the vaccinated-positive group were exposed to a positive household member (15 of 27 [56%])  compared with HCWs in both the nonvaccinated-positive (24 of 63 [38%]) and vaccinated-negative groups (7 of 81 [9%]; P <.001). Among the vaccinated healthcare workers who tested positive, the OR of exposure to a positive household member was 2.03 (95% CI, 0.74-5.62) compared with nonvaccinated-positive HCWs and 12.5 (95% CI, 3.70-43.23) compared with vaccinated-negative HCWs.

The study was limited by its small sample size and retrospective design. The investigators attempted to increase the study power by including 3 negative controls for each case.

The researchers concluded, “this case-control study found that exposure to SARS-CoV-2–positive household members was a risk factor associated with infection among vaccinated [HCWs].” Owing to these results, their hospital has implemented a policy of quarantining vaccinated HCWs who have had significant exposure to household members positive for SARS-CoV-2 infection. Further, they note that, given the emergence of the Delta variant in Israel and worldwide, “our proposal should apply not only to [HCWs] but to the general population.”

Disclosure: One study author declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.

Reference

Oster Y, Benenson S, Harpaz LY, et al. Association between exposure characteristics and the risk for COVID-19 infection among health care workers with and without BNT162b2 vaccination. JAMA Netw Open. 2021;4(9):e2125394. doi:10.1001/jamanetworkopen.2021.25394