London: A study conducted by researchers from the University of London has revealed that the antibody levels start to decrease six weeks after complete immunization with the Pfizer and AstraZeneca vaccine. The study published in the Lancet Journal also claimed that antibody levels reduce by more than 50% in 10 weeks.
The new research has raised serious concerns over the efficacy of vaccines, if the antibody levels decrease at this rate the immunity provided by the vaccine will decrease especially against the new variants. The study stressed the need for booster doses of vaccines.
The study claims that the antibody levels are substantially higher following two doses of the Pfizer vaccine than after two doses of the AstraZeneca vaccine. The antibody levels were also much higher in vaccinated people than those with prior SARS-CoV-2 infection.
The study was conducted among 600 people aged 18 and above. As per the study, for Pfizer, the antibody levels reduced from a median of 7506 Units per millilitre at 21-41 days to 3320 Units per millilitre at 70 or more days. For AstraZeneca, the antibody levels reduced from a median of 1201 Units per millilitre at 0-0-20 days to 190 Units per millilitre at 70 or more days.
‘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,’ said Madhumita Shrotri from UCL Institute of Health Informatics.
Also Read: First time in three months, India records less than 30,000 fresh COVID-19 cases
‘However, we found these levels dropped substantially over the course of two to three months. If they carry on dropping at this rate, we are concerned that the protective effects of the vaccines may also begin to wear off, particularly against new variants; but we cannot yet predict how soon that might happen,’ Shrotri said in a statement.
The findings support recommendations from the UK Joint Committee on Vaccination and Immunization (JCVI) that adults who are clinically vulnerable, those aged 70 years or over, and all residents of care homes for older adults should be prioritized for booster doses.
‘In addition, those who were vaccinated with the AstraZeneca vaccine, including most care home residents, are likely to have much lower antibody levels than those vaccinated with the Pfizer vaccine, so this may also need to be considered when deciding who should be prioritized when boosters are rolled out,’ said Professor Rob Aldridge from the UCL Institute of Health Informatics.
The researchers also made it clear that the study was conducted among a small sample size and different people will have different levels of immunity depending on the virus-neutralizing ability of their antibodies as well as their T-cell responses. So, additional research is needed to establish if there is an antibody level threshold needed for protection against severe disease.
Post Your Comments