Pfizer, AstraZeneca vaccine antibody levels may decline in 2-3 months, suggests Lancet study

The researchers believe that if the antibody levels carry on dropping at this rate, there will be concerns about the protective effects of the vaccines which may begin to wear off. 

According to a study published in The Lancet Journal, total antibody levels start to wane six weeks after complete immunisation with Pfizer and AstraZeneca vaccines and can reduce by more than 50 per cent over 10 weeks. The researchers believe that if the antibody levels carry on dropping at this rate, there will be concerns about the protective effects of the vaccines which may begin to wear off. 

The University College London Virus Watch study further stated that antibody levels are substantially higher following two doses of the Pfizer vaccine than after two shots of the AstraZeneca preventive, known as Covishield in India.

Madhumita Shrotri from UCL Institute of Health Informatics said that the levels of antibody following both doses of either the AstraZeneca or Pfizer vaccine were initially very high, which is likely to be an important part of why they are so protective against severe COVID-19. However, they found these levels dropped substantially over two to three months.

The findings were based on data from over 600 people aged 18 and above were consistent across all groups of people regardless of age, chronic illnesses or sex, according to the researchers. Researchers further noted that people who were vaccinated with AstraZeneca are likely to have much lower antibody levels than those vaccinated with Pfizer.

The team also acknowledged certain limitations in the data, including a small sample size for some groups. They said further research will be important to establish if there is an antibody level threshold needed for protection against severe disease.