Long Interval Between COVID-19 Vaccines Generates Up to 9 Times as Many Antibodies


Almost all the participants who had not had COVID-19 seroconverted after vaccination, meaning they made antibodies against the virus.

A longer interval between primary COVID-19 vaccine doses was found to boost antibody production up to 9 times, according to a study presented at the European Congress of Clinical Microbiology & Infectious Diseases.

Ashley Otter, MD, and colleagues measured antibody levels in blood samples taken from almost 6000 health care workers from across the United Kingdom as part of the UK’s SIREN study.

In the analysis, 3989 of 5871 participants received their first vaccine dose at least 21 days earlier and 1882 participants had their second dose at least 14 days earlier.

Each participant was classified by infection history as either previously having had COVID-19 or naïve, with no history of infection. Almost all the participants who had not had COVID-19 seroconverted after vaccination, meaning they made antibodies against the virus.

When analyzing dosing intervals (post-dose 1 and post-dose 2), it was discovered that longer dosing intervals was associated with antibody levels up to 9 times higher in naïve participants as well as showing a more pronounced effect in younger participants.

The dosing interval did not affect antibody levels in those with previous infection; however, a longer interval between infection and vaccination was linked to higher antibody levels. Participants who had their first dose of the vaccine 8 months after an infection had antibody levels 7 times higher than those who were vaccinated 3 months after infection, plateauing after 8 months. This suggested that 8 months after primary infection may be optimal for administration of the first vaccine in those with prior infection, according to the study authors.

The analysis also found that regardless of timing between infection and vaccination, all the individuals possess a very high antibody response after dose 2. Further, female participants and those from an ethnic minority were found to have significantly higher antibody tiers, whereas immunosuppression was associated with significantly lower post-vaccination antibody responses.

“This study shows that a longer time between vaccine dose 1 and dose 2 results in higher antibody responses in naïve participants, which strongly supports the decision by JCVI and the UK government to lengthen the interval between vaccine doses,” Otter said in a press release. “We’ve also shown that in those with previous infection, timing between exposure and vaccination plays a critical role in post-vaccination antibody responses. However, further research is needed to determine whether these higher antibody levels provide greater protection against COVID-19 disease and how this longer dosing interval may affect booster responses.”


Longer interval between COVID-19 vaccines generates up to nine times as many antibodies. EurekAlert! April 21, 2022. Accessed April 22, 2022. https://www.eurekalert.org/news-releases/950221

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