The study, which was published in the journal Epidemiology & Infection, followed 541 health care workers—some of whom had already recovered from COVID-19 infection—to see how those who had previously been infected with COVID-19 responded to vaccination compared to those who hadn’t.
Individuals infected with COVID-19 should be given a second dose of the vaccine soon after getting the first, according to research published recently by the Azrieli Faculty of Medicine at Bar-Ilan University and Ziv Medical Center.
The study, which was published in the journal Epidemiology & Infection, followed 541 Ziv Medical Center health care workers—some of whom had already recovered from COVID-19 infection—to see how those who had previously been infected with COVID-19 responded to vaccination compared to those who hadn’t.
In this collaborative study, health care workers at Ziv Medical Center, one of northern Israel’s leading hospitals, supplied blood samples on a regular basis to test their antibody levels after immunisation. Following a sample examination of people who were infected before and after vaccination, as well as those who were never infected, a number of differences emerged.
Individuals who had been previously infected and had only one dose of the vaccine had much greater IgG antibody levels than fully vaccinated workers who had never been sick. Infection after the first dosage (but before the second) did not raise IgG levels, and those infected after the first dose but not after the second had antibody levels comparable to those who got one dose but were never infected.
Individuals in the post-vaccination cohort had IgG antibody levels at 21 and 50 days that were equivalent to those who had never been infected and received the same number of doses, but significantly lower than those who had been infected prior to vaccination.
“Our study suggests that two doses of vaccine are needed in those who were infected shortly after the first dose,” says epidemiologist Prof. Michael Edelstein, of Bar-Ilan University’s Azrieli Faculty of Medicine.
“Although it was conducted on a small cohort, our data suggest that a second dose provides optimal protection to those patients infected between doses,” he adds.
Dr. Kamal Abu-Jabal of Ziv Medical Center and the Azrieli Faculty of Medicine, as well as a team of colleagues from the hospital and medical school, worked with Edelstein.
Larger studies are needed to validate or disprove the necessity for a second dose of COVID-19 vaccination in these patients, especially in the setting of new variations against which vaccines are less effective, according to the researchers.
The current findings are based on research published in the journal Eurosurveillance in February 2021. The researchers reported evidence that those previously infected with the virus responded very strongly to one dose of the Pfizer vaccine, regardless of when they were infected or whether or not they had detectable antibodies against COVID-19 prior to receiving the vaccine, in that study on the same cohort of health care workers.
Prof. Edelstein and colleagues are continuing to monitor the cohort’s antibody and immune system responses, as well as those who receive the third dose’s reaction.
More information: Kamal Abu Jabal et al, SARS-CoV-2 Immunogenicity in individuals infected before and after COVID-19 vaccination: Israel, January-March 2021, Epidemiology and Infection (2021). DOI: 10.1017/S0950268821001928
Kamal Abu Jabal et al, Impact of age, ethnicity, sex and prior infection status on immunogenicity following a single dose of the BNT162b2 mRNA COVID-19 vaccine: real-world evidence from healthcare workers, Israel, December 2020 to January 2021, Eurosurveillance (2021). DOI: 10.2807/1560-7917.ES.2021.26.6.2100096
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