Patrick Vallance warns less than 8% of public have antibodies
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According to the study, published in The Lancet, antibody count starts to wane six weeks after complete immunisation with Pfizer and AstraZeneca. Antibodies are important, as they bind to the surface of the virus to prevent it from invading a cell. However, it remains unclear how long COVID-19 antibodies last or to what degree they protect the body from the virus, according to the Centers for Disease Control and Prevention.
Madhumita Shrotri, from UCL Institute of Health Informatics, noted: “The levels of antibody following both doses of either the AstraZeneca or Pfizer vaccines were initially very high, which is likely to be an important part of why they are so protective against severe COVID-19.
“However, we found these levels dropped substantially over the course of two to three months.”
The study, named UCL Virus Watch, also found that antibody levels are substantially higher following two doses of the Pfizer vaccine, compared with the AstraZeneca jab.
The researchers noted that although the clinical implications of waning antibody levels remain unclear, current research shows the vaccines remain effective against severe disease.
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For the study, researchers from University College London, analysed data from 600 people aged 18 and above.
With the Pfizer vaccines, the researchers found that antibody levels, which were at 7506 units per millilitre between 21 to 41 days, dropped to 3320 units per millilitre after 70 days.
With the AstraZeneca vaccine, antibody levels reduced from 1201 units per millilitre between day 0 to 20, to just 190 units per millilitre after 70 days.
Professor Rob Aldridge, from UCL Institute of Health Informatics added: “When we are thinking about who should be prioritised for booster doses our data suggest that those vaccinated earlier, particularly with the AstraZeneca vaccine, are likely to now have the lowest antibody levels.”
The authors of the study noted that different people will have different immunity to the virus depending on their T-cell responses.
They said: “Even when measurable antibody levels are low, there is likely to be continuing immune memory that could offer long-term protection.”
B and T cells are white blood cells that work together to hunt down infections and remember how to fight them off.
According to previous research, B and T cell levels start to rise between one to six months after an infection has occurred, and then remain constant.
Doctor Dan Kaul, professor of infectious disease at the University of Michigan noted: “B and T cells are alive, so they can divide and turn into memory cells and other cell types that can last for many years and react when an infection is again encountered.”
Antibodies are not capable of reproducing, so their numbers tend to drop overtime, as the infection subsides.
Conversely, B cells will continue to sustain a certain level of circulating antibodies for a prolonged period of time.
Vaccines prompt the body to generate an immune response that’s specifically tailored to the particular variant that the vaccine is designed to emulate.
The daily number of COVID-19 cases in the United Kingdom has fallen for a seventh day in a row, to 23,511.
Boris Johnson earlier urged people to remain cautious and not jump to “premature conclusions” about the falling numbers.
Speaking of the latest figures, he said: “It’s very important that we don’t allow ourselves to run away with premature conclusions about this.”
Public Health England, stressed the pandemic “was not over yet” and urged people to still take precautions.
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