Antibody levels generated by two doses of the Oxford/AstraZeneca or Pfizer/BioNTech coronavirus vaccine may start to fall six weeks after the second jab, and for some could drop by up to 50 percent in less than three months, research suggests.
University College London’s (UCL) Virus Watch study analysed blood from 552 vaccinated people mostly in their 50s and 60s.
Antibody levels varied widely between patients, but a double dose of Pfizer/BioNTech produced more antibodies against the virus than two Oxford jabs.
For the Pfizer vaccine, antibody levels fell from an average of 7,506 units per millilitre (ml) at 21–41 days, to 3,320 units per ml at 70 or more days.
For the Oxford jab, they fell from 1,201 units per ml at 0–20 days to 190 units per ml at 70 or more days.
The findings are published in the results in a research letter to the Lancet.
The letter said it might be “important if antibody levels in some groups drop below (as yet undefined) thresholds of protection earlier than in others” as higher antibody levels are “possibly associated with greater protection against variants,” but also said that T-cell responses can possibly “compensate to some extent as antibody responses wane.” – READ MORE
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