Studies Reveal the Real Impact of COVID-19 Vaccines on Infection & Hospitalization

Three real-world studies conducted in the UK have confirmed that one or two doses of the Pfizer/BioNTech or AstraZeneca/Oxford COVID-19 vaccines are effective in preventing both symptomatic and asymptomatic infections and subsequent hospitalizations.

According to the study first carried out by the Public Health England (PHE), COVID-19 vaccines of Pfizer and AstraZeneca are up to 70% effective 21 days after the initial dose and 85% effective 7 days after the booster dose.

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23,234 adult healthcare workers from 104 public hospitals across England had enrolled for the PHE study which started on 7 December 2020, one day before the UK started rolling out the COVID-19 vaccine for the mass vaccination campaign.

35% of the study’s participants had either previously tested positive for COVID-19 or had developed antibodies against the viral infection while 65% had neither. The median age of the participants was 46.1 years. 84% of participants were women, 88% were White, and 86% worked directly with patients. Around 25% of the participants had an underlying medical condition, the most common of which were asthma, obesity, and diabetes.

In the follow-up period, PHE recorded only 8 COVID-19 infections per 10,000 persons within 21 days after receiving the initial dose of the vaccines and just 4 infections per 10,000 persons with 7 days after receiving the booster dose of the vaccines.

According to the second study conducted on a small scale by the Hull Teaching Hospital, both symptomatic and asymptomatic COVID-19 infections decreased significantly as Coronavirus vaccination increased from 8.3% on 4 January to 82.5% on 21 February.

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Only the hospital staff of the Hull Teaching Hospital participated in this study in which only Pfizer’s vaccine was administered. The staff were administered the first dose on 9 December and the second dose 12 weeks after the first. Just 13 staff members had tested positive for COVID-19 within 14 days after receiving the initial dose of the vaccines.

According to the third study conducted by the University of Edinburgh, COVID-19-related hospitalizations reduced substantially days after the first doses of the Pfizer and AstraZeneca vaccines were administered to adults in Scotland from 8 December 2020 to 15 February 2021

Edinburgh researchers evaluated the electronic health records of around 5.4 million people in Scotland registered at 940 general practice clinics, representing about 99% of the population.

For instance, only 723 out of 1.3 million people aged 65 on average were hospitalized due to COVID-19 infection despite getting vaccinated against the viral infection. Pfizer’s first dose was 91% effective and AstraZeneca’s first dose was 88% effective in reducing hospitalizations in this age group. For people aged 80 years or above, both vaccines proved to be 83% effective.