As nations around the world gain access to widespread COVID-19 vaccines, scientists are getting a clear picture of just how effective vaccines like Pfizer-BioNTech mRNA can be. Before recent weeks, vaccines had only been tested on smaller-scale groups of individuals which, while still showing promising results, provided challenges. For example, in phase three of Pfizer’s clinical trials, the control group of 21,720 individuals only consisted of a small subpopulation which excluded many groups of people.
While this previous study showed high efficacy, scientists were unable to include groups such as those with underlying health conditions and chronic illnesses. Now, for the first time since the approval of a vaccine against COVID-19, scientists are beginning to see results of mass vaccinations with 94% effectiveness. More major factors that could play a role in such large-scale studies are how well people stick to their vaccination follow-ups, and vaccine-handling logistics by healthcare providers and authorities.
The data used for the study was supplied by Clalit Health Services CHS, the largest healthcare organization in Israel, which insures 4.7 million patients. Conducted from December 20, 2020, to February 1, 2021, this study supplied the first real data scientists now have on the efficacy of nationwide vaccination. With such a large number of the Israeli population covered by CHS (53%), scientists were able to study data that spanned multiple age groups, sexes, races, ethnicities, and neighborhoods.
Before February 1, CHS had vaccinated 1,503,216 people, with 1,655,920 individuals not having been vaccinated. Of those individuals, 596,618 people from each control group were used for the study. A 1:1 ratio study meant that for every vaccinated person, an unvaccinated individual was paired with them as a control, and was on the same follow-up schedule. Pairs were made based on similar factors such as age, sex, and area of residence. The focus of this large-scale research effort was to track five different outcomes of vaccination effectiveness: documented infection, symptomatic infection, hospitalization, severe illness, and death. The results were as follows:
“In the follow-up period starting 7 days after the second dose, the vaccine effectiveness for documented infections, symptomatic illness, hospitalization, and severe disease was 92% (95% CI, 88 to 95), 94% (95% CI, 87 to 98), 87% (95% CI, 55 to 100), and 92% (95% CI, 75 to 100), respectively.”
Such a large-scale study shows incredible promise for other countries as well; scientists are beginning to see the effects of mass vaccinations in a “non-controlled” environment. With the possible approval of new vaccines, now, more than ever, there is hope in the ongoing fight against COVID-19.
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