12-Week Delay in Vaccine Boosts Immune Response

COVID-19 Vaccine

A study revealed an increased immune response in those who received the second dose of Pfizer vaccine after a 12-week delay.

COVID-19 vaccines have come to play a key role in pushing the world towards a pandemic-free future. The standard interval between vaccines is two to three weeks. However, multiple countries have increased this interval in an attempt to vaccinate more people with a single dose quicker. Thus, providing some level of protection to a greater population. The UK government also followed a similar route and delayed the second dose of Pfizer vaccine by 12 weeks in the elderly. Now, a study by the University of Birmingham in collaboration with Public Health England has found the delay in the vaccine may have actually helped boost the immune response as an added benefit.

This research is crucial, particularly in older people, as immune responses to vaccination deteriorate with age. Understanding how to optimise COVID-19 vaccine schedules and maximise immune responses within this age group is vitally important.

Dr Helen Parry, lead author

The researchers recruited a total of 172 participants aged 80 years and above who lived independently. They all received two doses of the Pfizer vaccine; either with the standard 3-week interval or a delayed 11 to 12-week gap. Two weeks after the second dose, the researchers measured antibody levels in the participants to gauge the immune response.

Antibody Response was 3.5 Times Greater

The results showed that a delay in vaccine caused 3.5 times higher antibody response as compared to those who received the vaccine after the standard 3-week timeframe. According to lead author, Dr Helen Parry their study reveals that a 12-week delay enhances the peak antibody response in older people. This is a highly significant finding since immune responses to vaccines tend to decline with age.

However, the cellular immune response was lower in the vaccine delay group. A cellular immune response uses killer T-cells to destroy pathogens. Another subset, the Helper T cells help activate other immune cells important for generating antibodies. It is unclear as to why the 12-week interval group had a weaker cellular immune response.

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

Paul Moss, study author

The study is not peer-revied and is available at the pre-print server medRxiv.


Parry, H, et al. “Extended Interval BNT162b2 Vaccination Enhances Peak Antibody Generation in Older People.” 2021, doi:10.1101/2021.05.15.21257017.


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