A study published in The Lancet journal says that the total antibody level starts to become weaker after completing immunization with AstraZeneca and Pfizer vaccines. Also, the antibody levels may reduce by over 50 per cent over 10 weeks or 2-3 months.
As per the University College London (UCL) researchers, if the antibody levels begin to drop at this rate then protective effects of the vaccines may also wear off. They added that but how soon that might happen cannot be predicted yet.
The University College London Virus Watch study also found that antibody levels are considerably higher after two doses of the Pfizer vaccine compared to two shots of the AstraZeneca jab (Covishield).
Madhumita Shrotri from UCL Institute of Health Informatics statement, “The levels of antibody following both doses of either the AstraZeneca or Pfizer vaccine initially very high, which is likely an important part of so protective against severe Covid-19.”
Findings consistent across all groups of people
According to the data collected for more than 600 people aged 18 and above, the findings of the study remain consistent among all groups of people, regardless of chronic illnesses or sex, age, researchers said.
For Pfizer, antibody levels reduced from a median of 7506 units per milliliter (U/mL) at 2141 days, to 3320 U/mL on 70 or more days. And, if we talk about the AstraZeneca vaccine, antibody levels got reduced from a median of 1201 U/mL at 20 days to 190 U/mL at 70 or more days, over a five-fold reduction.
Professor Rob Aldridge from UCL Institute of Health Informatics said “When we are thinking about who should be prioritized for booster doses, our data suggests that those vaccinated earliest, particularly with the AstraZeneca vaccine, are likely to now have the lowest antibody levels.”