More than half of healthcare workers vaccinated against COVID-19 who later tested positive for the virus were exposed to an infected member of their household, a study published Wednesday by JAMA Network Open found.
Fifteen of 27 vaccinated health workers in the study were infected after being exposed to the virus at home, as opposed to on the job, at which many treated patients with COVID-19 wore protective equipment to limit spread, the data showed.
However, the 27 cases were the only ones identified among more than 5,300 vaccinated health personnel, an infection rate of 0.5%.
Conversely, 69 of 690 unvaccinated staff later tested positive for the virus, according to the researchers.
Although the study focused on healthcare workers, its findings “are very important to everyone’s daily behavior [in] that the vaccine’s protection is not absolute — when the exposure is close and prolonged,” study co-author Dr. Yonatan Oster told UPI in an email.
“With positive household members, the risk of getting infected is high,” said Oster, acting head of the infection prevention and control unit at Hadassah Medical Center in Jerusalem.
Based on their findings, the researchers feel that even vaccinated people who have been exposed to the virus through an infected member of their family should be quarantined in order to prevent further spread.
Although tests of vaccination effectiveness against older strains of the virus indicated that they provided more than 90% protection against severe disease, newer data suggest that they provide less than 70% protection against the Delta form.
According to the researchers, the new study examined infection rates and virus exposures among Hadassah Medical Center workers.
By March 31, 5,312 medical centre staff had received both doses of the Pfizer-BioNTech vaccine, leaving 690 unprotected.
Eight of the 27 vaccinated workers who tested positive for COVID-19 were assigned to a department that treated virus patients.
However, based on contact tracing, only two of these 27 positive cases among vaccinated staff could be linked with on-the-job exposures.
Among vaccinated staff who tested positive for the virus, the most common symptoms were nasal inflammation, sore throat, cough and loss of sense of taste or smell.
According to the researchers, just one of the 27 COVID-19 instances among vaccinated personnel required hospitalisation.
As of the end of March, no one in the study’s personnel, vaccinated or unvaccinated, has died from the virus.
The study focused on the period preceding the emergence of the Delta version of the coronavirus in Israel.
“The healthcare personnel in our study were primarily exposed outside of the facility,” Oster explained.
“The danger in household exposures is substantially higher, even for vaccinated people,” he says, “since we normally don’t utilise preventative measures at home [such as] masking and distance.”