A fourth dose of the coronavirus vaccination significantly lowered the chances of infection and serious illness in patients 60 years of age and older, according to a peer-reviewed study conducted by Clalit Health Services and Harvard University and published in The New England Journal of Medicine on Wednesday.
Between two weeks and one month after receiving the fourth dose, patients were 52% less likely to be infected compared to those who received just the third dose at least four months earlier.
Patients were also 61% less likely to experience symptomatic infection, 72% less likely to be hospitalized, 64% less likely to experience severe illness and 76% less likely to die compared to those who received just the third dose at least four months earlier.
This is the first study to evaluate the effectiveness of the fourth vaccine dose in preventing all sorts of coronavirus illness.
The study examined data from 182,122 patients who are 60 or older who received the fourth dose. Data from a control group of 182,122 patients of the same age who received only the third dose at least four months earlier without receiving the fourth dose were also examined as part of the study.
The PCR testing rates between the two groups were similar.
The study was led by Dr. Uri Magen, Dr. Jacob Waxman and Dr. Maya Makov Assif, who specialize in public health in the innovation framework at Clalit. The study examined data from between January 3 to February 18, 2022, while the Omicron variant was dominant in Israel.
“The results from the fourth vaccination campaign for those ages 60 and over clearly demonstrate that the fourth vaccine dose significantly protects against coronavirus disease complications – including a fourfold reduction in the risk of mortality compared to those who received a third dose over four months ago,” said Prof. Ran Balicer, chief innovation officer at Clalit Health Services and founding director of the Clalit Research Institute.
“The results of the study can help every person make an informed decision about the need for a vaccine according to personal risk,” added Balicer. “In our estimation, the results of the study will lead the elderly population and those at risk of disease complications to choose to be vaccinated with the fourth dose, in any country in the world where the virus continues to spread in the community.”
Dr. Roni Vered, Clalit’s chief physician in the Tel Aviv District, said, “The community medical teams once again succeeded in leading an extensive vaccination operation in a short time for a vulnerable population, and the data obtained from the study demonstrate that the vaccination operation saved the lives of the elderly and vulnerable population.”
Dr. Dror Dicker, head of internal medicine at the Rabin Medical Center, said, “The wave of morbidity due to the Omicron strain has been a huge challenge for medical teams, and the research data allow us to understand the extent of hospitalization and serious illness prevented due to the vaccine operation. The results substantiate the call for those who are in the relevant age group and have not yet received the fourth dose – to go out and get vaccinated.”
Prof. Ben Reis, director of the Predictive Medicine Group and a member of the faculty of Harvard Medical School and the Boston Children’s Hospital Computational Health Informatics Program, explained, “Currently, one of the main reasons for hesitation regarding receiving the fourth vaccine dose is a lack of information regarding its effectiveness. The punctilious epidemiological research presented before us provides reliable information regarding the effectiveness of the vaccine. We hope the study will help in reaching a decision for those who are in the risk group and have not yet been vaccinated with the fourth dose.”
Earlier this month, another study by Health Ministry officials published in The New England Journal of Medicine found that a fourth dose of the COVID-19 vaccine provides people ages 60 and up with three times greater protection from serious illness.
A study in March by Sheba Medical Center found that the fourth dose of the vaccine offered little extra protection against infection among young and healthy individuals compared to just three doses. However, it did find that a fourth dose provided moderate protection against symptomatic infection among young and healthy individuals.
Another study in March by Clalit found that the fourth dose resulted in a 78% decrease in COVID-related deaths in adults ages 60-100.