How effective was the vaccination program COVID-19 in Israel?

According to the publicly available coronavirus disease 2019 (COVID-19) data from Israel, a study suggests that the BioNTech-Pfizer BNT162b2 vaccine appears to be very effective in the real world.

Several vaccines have now been approved for COVID-19, and many countries have started intensive vaccination programs. In Israel, the vaccination began on December 20, 2020. By the end of January, 33% of the population had received the first dose of BioNTech-Pfizer vaccine, also known as BNT162b2, and 19% had received their second dose.

Just as the vaccinations began, the country was in the middle of a third wave of COVID-19, with cases and hospitalizations more than doubling by mid-January 2021. In response, the country declared an exclusion on January 8, 2021. cases did not come down, and there were questions about the effectiveness of the vaccine.

However, it is challenging to estimate how effective vaccines are in the real world. The survey of vaccinations includes the socio-economy and demographics of a population, together with the differences in infection rates between groups. Such confusing factors are not present in randomized clinical trials due to blindness. In the real world, clinical and demographic data at the individual level are needed to determine the effectiveness of the vaccine.

Estimation of the effectiveness of the vaccine

In an article published on the medRxiv * preprint server, assistant professor Dvir Aran, of the Technion-Israel Institute of Technology, used publicly available data on COVID-19 cases and hospitalization after vaccination by the Pfizer vaccine. The author provides estimates of the efficacy of vaccines in reduced cases.

The author uses the daily positive cases and hospitalization data from the Israeli database of the Israeli Ministry of Health COVID-19, including hospitalization after vaccination until January 31, counts the number of vaccinations each day and multiplies it by the daily case rate of the whole. population, and adjust for the difference in the number of cases between the vaccinated and general population. Based on these parameters, the author estimated the effectiveness of the vaccine.

According to the analysis, there were 3082,190 people who were vaccinated with a first dose between 20 December 2020 and 31 January 2021, and 1 789 836 also received their second dose. Of the total vaccinated, 1,215,797 were older than 60 years.

Among those vaccinated, 31,810 tested positive for SARS-CoV-2 and 1,525 were hospitalized or died. The analysis indicates that there was a 28% reduction in the number of cases for those over 60 years of age on day 13 after the first dose, a 43% reduction between days 14 and 21, and a decrease of more than 80% after the second dose.

This analysis is based on the assumption that all people who received their vaccinations early had the same level of positive cases as the general population. But this is not true in the real world. Older people have lower positivity and lower socio-economic groups have higher positivity rates.

Adapting to this, the author found that if it is assumed that the vaccinated population has half the number of cases as the general population, there is no decrease in the number of cases up to 21 days after the first dose. The number of cases decreased by 66% seven days after the second dose.

For people older than 60 years, which accounts for a large proportion of the severely ill cases, the analysis indicates a strong effect of the vaccine, which reduces severe cases by about 60% after the first dose and up to 94% seven days after the second dose.

Vaccination is very effective in the real world

Overall, the analysis indicates a decrease in positive cases of 66-83% in people older than 60 years, 76-85% for those under 60 years and 87-96% effective in preventing severe cases.

The Pfizer vaccine is said to be 95% effective one week after the second dose based on clinical trials, although its effectiveness is not clear. Analysis of actual data from Israel, which includes about 140 times more individuals than the trial, provides an estimate of the vaccine’s effectiveness in reducing cases and the severity of the disease.

The author acknowledges some limitations of the analysis. These include delays in reporting cases, the fact that hospitalization can increase the number of cases observed, and limitations on the derivation of individual levels as the analysis used to collect scores. Since the prevalence in the general population is also affected by vaccination, the actual effectiveness may be higher. The author writes that the analysis gives a strong assurance that the vaccine is very effective.

* Important notice

medRxiv publishes preliminary scientific reports that are not judged by peers and therefore should not be considered conclusive, should guide clinical practice / health related behavior, or should be treated as established information.