Clalit Health Fund study examined the effectiveness of the vaccine for recovering patients, preventing the re-infection of the virus and found that there was an 82% reduction in the risk of re-infection with the coronavirus aged 16-64 vaccinated in one dose after recovery from the coronary, and a 60% reduction among those aged 65 and over
A new study by Clalit, which examined the effectiveness of vaccinating corona recoverers in preventing re-infection with the virus, shows that there is an 82% reduction in the risk of re-infection with the corona virus among 16-64-year-olds vaccinated for the first time after corona recovery and a 60% reduction among those aged 65 and over.
This is a study published today in the leading medical journal New England Journal of Medicine. The study was led by the Department of Medicine in the Clalit Community Division in collaboration with the Faculty of Health Sciences at Ben-Gurion University of the Negev and the Laboratory for Maximizing Health Outcomes at Sapir College.
The research team analyzed the data of Clalit’s patients using advanced statistical methods to examine the effectiveness of Pfizer’s BNT162b2 company in preventing re-infection with the virus among Corona recoverers who received the vaccine at least three months after their recovery.
It is known that the risk of contracting the corona virus is significantly reduced among corona recoverers, but it has not yet been known how long this protection survives. Following this, the Ministry of Health in Israel recommended that those who have not yet been vaccinated recover from a single vaccine dose – three months after their recovery. However, the benefit of the recovering vaccine has not yet been tested on a significant population, until the publication of this study. Receiving one dose of vaccine is a condition for receiving a “green mark” for recoverers.
The observational study followed all Clalit patients, aged 16 and over, who recovered from Corona and at least three months after their recovery, and compared the rates of re-infection in Corona in the population that received one or more vaccines after recovery, compared to the re-infection rates among recovering patients who were not vaccinated at all.
The follow-up was carried out between March 1, 2021, the date on which the Ministry of Health approved the vaccination of recovering people from Corona until November 26, 2021, towards the end of the delta wave in Israel.
The researchers reviewed data from 149,032 Clalit patients who had recovered from coronary heart disease. They were divided into two groups dynamically, based on the status of receiving the vaccine. The research method included a multivariate regulation for a variety of risk factors, in order to neutralize possible biases that could result from age, gender, socioeconomic status differences, or comorbidities between populations. Due to the wide size of the groups it is possible to provide an accurate estimate of the relationship between receiving the vaccine dose and the rates of re-infection with the corona virus, especially during the delta wave period.
The research findings:
The mean age of the study population was 39. At the end of the study period, 56% of the recovering population received at least one vaccine dose.
Among vaccine recipients (one week or more after receiving the vaccine), an 82% reduction in SARS-CoV-2 re-infection rate was observed among 16-64-year-olds; And a 60% reduction in recurrent infections aged 65 and over – compared to recoverers of those ages who were not vaccinated at all.
It should be noted that according to the results of this study, no benefit was found for giving two vaccines to recoverers, over giving one vaccine.
This finding supports the guidelines of the Ministry of Health in Israel, to be satisfied with one vaccine for recovering people.
According to Dr. Doron Netzer, Head of the Community Medicine Division at Clalit: “Even before the outbreak of the fourth wave of infection from the Delta strain, the health authorities in Israel and around the world also instructed to vaccinate patients who had recovered from Corona. This guideline was given that since after recovery from corona antibodies are formed in the body but due to the lack of evidence-based information for the duration of this protection, it was recommended that vaccinators be given vaccine as well. This is the first significant study that shows that corona recoverers also benefit from this vaccine. ”
“The results of our study show unequivocally that giving Corona vaccine to recoverers is significantly associated with reducing the risk of re-infection. Note that this information was correct during the Delta Wave period. Health as early as March 2021 to vaccinate recovering people has been very helpful in curbing the delta wave for all its implications.We hypothesize that the least benefit observed among people aged 65 and over was due to recovering from corona at these ages, tended to adhere much more to social alienation rules “Relatively, the additional protection from the vaccine is less, but still very significant.”
Dr. Netzer adds that “These findings, published in one of the world’s leading medical journals, provide important and well-established information to the population in Israel and around the world, some of whom still believe that protection after infection is sufficient to prevent re-infection and the results of this study show “.
The study was conducted on the basis of Clalit’s computerized databases, in accordance with the approval of the Institutional Helsinki Committee. The study was conducted without support from any external source.