Antibodies timescale22 Jul 2021 20:24
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% in less than three months, research suggests.
However, while antibodies are expected to wane this does mean people are less protected against the virus.
It is also not known how quickly the concentrations can increase again in the face of infection, something referred to as memory response.
UCL’s 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 Pfizer vaccine antibody levels fell from an average of units per millilitre (ml) at 21–41 days, to 3320 units per ml at 70 or more days.
For the Oxford jab they fell from 1201 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 authors write: “In the context of recent advice in support of booster vaccinations from the UK’s Joint Committee on Vaccination and Immunisation, and given the potentially rapid S-antibody decline suggested by these data, heterologous regimens, which preliminary data suggest elicit stronger antibody and T-cell responses, might provide more durable immunity and greater protection against emerging variants.