Story at a glance

  • Waiting between 21 to 55 days before receiving the second COVID-19 shot could boost antibody counts, per a new study.
  • Researchers focused on the Pfizer vaccine.
  • Results suggest a longer dosing interval could help fight the delta variant.

Longer intervals of time in between COVID-19 vaccination shots can help build stronger immunity against the delta variant, results from a new study released earlier this week indicate.

For the study, published Wednesday in the New England Journal of Medicine, researchers from Oxford University used a test-negative case-control — which utilizes volunteers who have tested negative for a COVID-19 infection to be control specimens — to estimate how effective the vaccine is against the variant and compared them with people who tested positive for an infection.

This method helped researchers control for any biases or confounding variables in its population. 

When measuring the effectiveness of the vaccine against the delta variant in comparison to the less-contagious alpha variant, the results found that after two doses, the vaccine provided protection against both variants with little difference. 

If the shots were administered within an approximate eight-week interval, or between 21 to 55 days, the protection offered by the vaccine is optimal. 

“What we found was, on average, if you had a shorter dosing interval, you had lower antibodies,” Susanna Dunachie, a professor of Infectious Diseases and study leader told Al Jazeera.

Overall, the estimated vaccine efficacy for people who received both doses of the Pfizer vaccine provided an efficacy of 88 percent against the delta variant and a stronger 93.7 percent against the alpha variant. 

The longer gap between vaccine shots may encourage greater development of neutralizing antibodies and other immune system responses, particularly T-cells. 

Patients who had a shorter gap within the three to four week standard reportedly saw T-cell levels that were higher, but those who waited longer to get the second dose had higher counts of more helpful, immunizing cells that support longer-term immune health. 

“Following two vaccine doses, neutralising antibody levels were twice as high after the longer dosing interval compared with the shorter dosing interval,” the authors reportedly said.

Published on Jul 23, 2021