At the same time, the researchers make a reservation and say that at this stage it is not possible to accurately estimate the rate of decrease in the effectiveness of the vaccine. Their assessment is that the effectiveness of the vaccine does not decrease drastically, since there is no widespread spread of the South African variety and it is very rare in Israel
The first study of its kind, states that the strain of the corona originating in South Africa succeeds to a certain extent in breaching the protection of the two doses of the Pfizer vaccine. Therefore, the expected protection of the vaccine against this strain is less than the good protection of the vaccine against the original strain of the corona and against the British strain, which is currently the most common infection in Israel. At the same time, the researchers make a reservation and say that at this stage it is not possible to accurately estimate the rate of decrease in the effectiveness of the vaccine. Their assessment is that the effectiveness of the vaccine does not decrease drastically, since there is no widespread spread of the South African variety and it is very rare in Israel.
The study was conducted as a collaboration between researchers from the Klalit Research Institute and Tel Aviv University. The research was led by Prof. Shai Ben Shahar, director of the personalized medicine department in the general innovation system, Dr. Doron Netzer - head of the medical department in the general community division, and Prof. Adi Stern From the Shmunis School of Biomedical and Cancer Research at the Faculty of Life Sciences at Tel Aviv University.
The researchers located Klalit patients who were found to be positive for corona starting 14 days after receiving the first vaccine dose. It should be noted that the high efficiency of the corona vaccine led to the fact that a very low number of vaccinated people were infected with corona, and after their detection, to each vaccinated person who was found to be positive for corona, a non-vaccinated person who was similar to him in age, sex, sector, area of residence and other characteristics was "attached". The study was based on about 800 subjects (about 400 pairs) of vaccinated and non-vaccinated people who were found to be positive for Corona, and all the viruses that were isolated were sent for genetic sequencing.
In the genetic sequencing it was found that the prevalence of the South African variety is low - about 1% of all the viruses that were sequenced among all those infected. Between the two groups infected with Corona, it was found that among those vaccinated with two doses, the frequency of the South African variety was significantly higher (8 times) than among the combined group from among the unvaccinated - in which the British variety and the original variety were more common. This means that the vaccine in 2 doses probably does not provide the same protection against the South African strain of the corona virus compared to the other variants. These results indicate that although the South African strain has a certain ability to break through the protection against infection provided by the Pfizer vaccine, but in light of the fact that the virus does not spread quickly in Israel, this ability may be limited.
In addition, the study tested how successful the British strain is in breaking through the immune system compared to the original strain of the corona virus. The data shows that among 250 corona positive carriers who were partially vaccinated (from two weeks after receiving the first dose to one week after receiving the second dose), it was found that the prevalence of the British strain was significantly higher compared to positive carriers who were not vaccinated, where the prevalence of the original strain of the corona was higher. This means that among carriers who were not vaccinated, it was possible to see more positive cases of corona of the original type, which the vaccine was aimed at in the first place.
It is important to note that after two doses of the vaccine, the proportion of the British strain among the vaccinated decreased significantly. This means that the British variety succeeds to some extent in breaking through the protection of the first weeks after one dose of vaccine, but this phenomenon is not observed a month later, after receiving the second dose.
The encouraging side: low prevalence of the South African variety
"We tested the resistance of the different variants in Israel - the British and the South African - to the Pfizer vaccine," explains Prof. Stern, from the Shmenis School of Biomedical and Cancer Research in the Faculty of Life Sciences at Tel Aviv University, "we tested whether we see more infections of a certain strain among the vaccinated compared to non-vaccinated, and we found the answer to this to be positive: we found, significantly, more cases of the South African strain among those vaccinated in the second dose, compared to the control group. This means that the South African variety can break through the immune defense to some extent. At the same time, it should be emphasized that the South African strain constitutes the minority of cases among the vaccinated population." According to Prof. Stern, "It is not possible to learn directly from the research the exact degree of protection of the vaccine against the South African strain, this is because the prevalence of the South African strain in Israel is very, very low, and represents approximately 1% of all infections. The low incidence is nevertheless very encouraging, because it means that even if this strain succeeds in breaking through the vaccine, it does not succeed in spreading in the population, as the British strain did, which makes up the overwhelming majority of corona infections in Israel."
According to Prof. Ben Shahar, director of the department of personalized medicine in the overall innovation system, "the results of this study illustrate the importance of expanding the genetic sequencing of the virus among those who are infected, in order to be able to locate a possible outbreak of the South African strain, as well as new strains in Israel, and to improve the isolation of patients carrying these strains. The results emphasize that the corona epidemic cannot be regarded as a situation that has passed."
Need for constant monitoring for new varieties
According to Dr. Doron Netzer, Director of the Medicine Division in the General Community Division, "This is the first study in the world, very important, based on "real world" data, which proves that the vaccine provides less protection against the South African strain compared to the original virus and the British strain. The results show the importance and need for continuous screening and monitoring for new strains and the use of additional measures, including distancing and masks in closed spaces, to prevent infection and to prevent another outbreak of corona in Israel."
Prof. Ran Blitzer, Head of the General Innovation Unit and Director of the General Research Institute, adds "The research method we applied in the first study of its kind, in which we sent 400 pre-paired pairs of vaccinated and non-vaccinated people with similar characteristics who were infected with Corona, allows us to overcome biases and draw conclusions. Although the numbers are not large and the scope of follow-up should continue to be expanded, the significant difference in the prevalence of the South African strain between the vaccinated who were infected despite the vaccination and the non-vaccinated indicates with a high probability that the vaccine is less effective in preventing infection with this strain. The reports so far on this issue from around the world have not been conclusive, but with all the necessary caution it can be said that the compatibility of this finding with laboratory findings of neutralization tests published in the world and in Israel requires attention, and emphasizes the need for a focused effort to expand the epidemiological-sequential monitoring and to intervene to reduce the further spread of the southern strain - an African in Israel".
The research results are published as a draft article on medrxiv.com after being submitted for peer review.
More of the topic in Hayadan:
