On December 13, 2021, an article was published in the prestigious journal Nature showing that although the combination of natural infection with SARS-CoV-2 along with vaccination (hybrid immunity) provides strong protection against the new coronavirus, a recent analysis of a large number of individuals from Israel argues that protection and hybrid immunity are gradually declining. Professors of the National and Kapodistrian University of Athens Ourania Tsitsiloni, Evangelos Terpos, Ioannis Trougakos and Thanos Dimopoulos (Rector of EKPA) summarize the main points of the study.
hybrid immunity or vaccine-enhanced immunity (3rd dose) is probably the "key" to preventing re-infections as well as serious infections from the Omicron variant
Hybrid immunity or hyper-immunity refers to people who have been infected with SARS-CoV-2 and co-vaccinated. This combination was rated as more protective compared to natural infection or vaccination alone. Although the study was performed before the appearance of the Omicron variant, its results provide important evidence for the development of protective immunity.
To date, laboratory analyzes of anti-SARS-CoV-2 antibodies have shown that individuals with hybrid immunity produce higher levels of neutralizing antibodies than individuals who have only been infected or only vaccinated, and in particular, neutralizing antibodies to hybrid immunity have a greater ability to inactivate the coronavirus.
An earlier study in Israel also showed that hybrid immunity protects the body better than 2 doses of vaccine. In order to determine the protective advantage of hybrid immunity, in the period August-September 2021, more than 5.7 million Israelis were studied, they were divided into 3 groups: (1) those who were infected with the virus and were not vaccinated, (2) those uninfected and vaccinated with 2 or 3 doses of vaccine, and (3) those who had recovered from SARS-CoV-2 infection and had been vaccinated with 1 dose of vaccine.
Although an increase in cases was observed in all groups during the above two months, people with hybrid immunity had 7 times lower rates of infections compared to those who received the 2nd dose of the vaccine 6-8 months ago and in addition, the hybrid immunity appeared to provide longer-lasting protection, although antibody levels gradually decreased in this case as well.
This study is the largest available to date, but has been challenged by the scientific community because, on the one hand, the number of people with severe COVID-19 in all groups was very small and, on the other hand, the demographics of participants in each group was different.
Despite the controversy, the main conclusion of this large study in Israel is that hybrid immunity or vaccine-enhanced immunity (3rd dose) is probably the "key" to preventing re-infections as well as serious infections from the Omicron variant. And certainly, its results will help Public Health Protection experts determine which is the most effective vaccination regimen to ensure the health of the population. At present, it is not yet known whether hybrid immunity is more protective than vaccines against the Omicron variant. The spread of the Omicron variant has increased the need for a majority of individuals to receive an additional booster dose, according to the study.