Study: Pfizer vaccine proves effective 12 days after 1st jab
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The National Institute of Infectious Diseases (NIID) on May 14 reported Pfizer’s COVID-19 vaccine lowers the chances of a recipient contracting the virus after about 12 days of the first shot.
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Of 1,101,698 health care workers who had received at least one shot of the Pfizer vaccine, 281 newly tested positive for the novel coronavirus afterward, according to a study.
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The institute announced the findings at a health ministry meeting the same day.
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The institute analyzed data from two systems of the central government that compile the vaccination situation and the information of those infected.
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During a period from the day of the inoculation until Day 13, the number of people who contracted the virus per 100,000 people was 1.26.
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But from Day 14 to Day 20, the number fell to 0.53. The number continued declining to 0.49 between Day 21 and Day 27, and 0.18 after Day 28.
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The number started declining after around Day 12, the institute said.
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In general, it takes a certain number of days after receiving a vaccine shot for a recipient to develop neutralizing antibodies that help prevent infections after inoculations.
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But the institute said there are many factors that have yet to be considered, such as differing infection situations because of regions and the time of year when vaccinated.
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The institute said further analyses are needed.
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