New research: For Covid-19 survivors, one dose of Pfizer vaccine as good as two for others

New research suggests that the second dose may not be needed for individuals who have successfully recovered from a prior coronavirus infection.

The Pfizer-BioNTech vaccine against SARS-CoV-2, part of the vaccination programme in a number of countries including the United States, is normally administered in two doses, 21 days apart. Now, new research suggests that the second dose may not be needed for individuals who have successfully recovered from a prior coronavirus infection.

The study, conducted by researchers at Cedars-Sinair Medical Center, Los Angeles, has been published in the journal Nature Medicine.

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Researchers administered surveys to 1,090 healthcare workers in the Cedars-Sinai Health System who had received the Pfizer-BioNTech vaccine. The surveys asked the workers about prior coronavirus infections and any symptoms they might have experienced after being vaccinated.

The healthcare workers also took antibody tests to gauge the response of their immune systems to the vaccinations. Antibody levels were measured at three points in time: before or up to 3 days after the first dose, within 7–21 days after the first dose, and within 7–21 days after the second dose.

Based on the surveys, the research team identified 35 individuals with prior coronavirus infections who had received a single vaccine dose, and 228 individuals without prior infection who had received both vaccine doses. Based on the antibody tests, the team found that levels and responses of coronavirus-specific antibodies were similar in both of these groups.

After the first dose, post-vaccine symptoms were more prominent for those with prior infection. After the second dose, symptoms were similar between the two groups, the study found.

Limitations

In a press release on the research, Cedars-Sinai Medical Centre mentioned a number of limitations in the study as acknowledged by the researchers.

It said the researchers noted that more research will be needed to confidently guide vaccine policy. They measured antibody levels only up to 21 days following each vaccine dose and that longer-term follow-up likely would provide additionally informative data, especially regarding the duration of the immunity acquired from receiving a single versus double dose of the vaccine.

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The researchers also noted that larger cohort samples will be needed to examine differences across demographic and clinical subgroups that are known to exhibit variation in antibody response following vaccination. More studies are needed to determine if the results seen after a single dose of the Pfizer-BioNTech vaccine might also apply to other SARS-CoV-2 vaccines, they added.

Source: Cedars-Sinai Medical Center, Los Angeles

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