ABOUT THE STUDY
The study, led by researchers at University College London, showed that the decreasing effect of the vaccine doses. It was constant in all groups of peopleregardless of age, chronic illness or gender.
Posted as a research letter in The Lancet, the study included data from more than 600 people. In addition, it showed that antibody levels are substantially higher after two doses of the Pfizer vaccine than after two doses of AstraZeneca.
The decrease was expected at Pfizer and AstraZeneca
They are also much higher in those with previous SARS-CoV-2 infection.
The researchers noted that although the clinical implications of lowering antibody levels are still unclear. Some decline was expected and current research shows that vaccines are still effective against severe disease.
For Pfizer, antibody levels fell from a median of 7506 U / mL at 21-41 days, to 3320 U / mL at 70 days or more. For AstraZeneca, antibody levels decreased from a median of 1201 U / mL at 0-20 days to 190 U / mL (67-644) at 70 days or more.
Will the protective effects suffice?
“Antibody levels after both doses of the AstraZeneca or Pfizer vaccine were initially very high. Which is probably an important part of why they are so protective against severe Covid-19. “ Said Maddie Shrotri of the UCL Institute of Health. Computing.
“However, we found that these levels decreased substantially over the course of two to three months. If they continue to decline at this rate. We are concerned that the protective effects of vaccines may also start to wear off, particularly against newer variants. But we still can’t predict how soon that will happen, ”he added.
Older, the most vulnerable group
The findings support the recommendations of the UK Joint Committee on Vaccination and Immunization (JCVI). That of adults who are clinically vulnerable. Those aged 70 and over and all residents of nursing homes for the elderly should have priority for booster doses.
Also, it is likely that those who were vaccinated with the AstraZeneca vaccine. Including the majority of nursing home residents. Have much lower antibody levels than those vaccinated with the Pfizer vaccine. So this must also be taken into account when deciding who should be prioritized when reinforcements are implemented. ” Said Professor Rob Aldridge of the UCL Institute for Health Informatics.
More studies are still needed
However, the study included only a small sample size and different people will have different levels of immunity. This depending on the ability of the virus to neutralize its antibodies. As well as their T cell responses.
Therefore, more research is important to establish whether there is a threshold level of antibody necessary for protection against serious disease, the researchers noted.
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