Delaying second Pfizer vaccine dose may protect better against COVID-19: study

May 14 2021, 10:27 am

Antibody response in people aged over 80 is three-and-a-half times greater in those who have the second dose of the Pfizer COVID-19 vaccine after 12 weeks, compared to those who have it at a three-week interval, according to a new study.

In collaboration with Public Health England, the study, led by the University of Birmingham, looked at 175 people over 80 years old who lived independently and compared the immune response between those given the second Pfizer vaccine at three- and 12-week intervals.

The study’s authors noted that the Pfizer vaccine was originally authorized for a three-week interval between doses. However, several countries, including the UK, chose to expand this to a 12-week interval to allow a higher percentage of the population to receive one vaccine dose quicker.

The research oversaw the team taking blood samples for analysis in the lab after participants’ first vaccine and then again two to three weeks after participants had received their second vaccine. Of the cohort, 99 participants had the second vaccine at three weeks, while 73 had the second dose at 12 weeks.

The research found that extending the second dose interval to 12 weeks increased the peak SARS-CoV-2 spike specific antibody response three-and-a-half-fold, compared to those who had the second vaccine at three weeks.

Although the peak cellular immune responses were lower after the delayed second vaccine, responses were comparable between the groups when measured at a similar time point following the first dose.

Researchers concluded that extending the administration of the second Pfizer vaccine to 12 weeks potentially enhances and extends antibody immunity, which is believed to be important in virus neutralization and prevention of infection.

“The enhanced antibody responses seen after an extended interval may help to sustain immunity against COVID-19 over the longer term and further improve the clinical efficacy of this powerful vaccine platform,” said the study’s corresponding author Professor Paul Moss.

These findings “may be important in the development of global vaccination strategy as [an] extension of [the] interval of the second vaccine dose in older people may potentially reduce the need for subsequent booster vaccines,” Moss added.

The research, which has been published as a preprint and therefore not yet peer-reviewed, was jointly funded by UK Research and Innovation (UKRI) and the National Institute for Health Research (NIHR) and supported by the British Society for Immunology.

Eric ZimmerEric Zimmer

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