People who have had Covid-19 may not require a second vaccination dose in the short term, researchers say.

A trial involving both the Pfizer and Oxford vaccines found that those who had already had the virus had a 59-fold higher antibody count that patients with no infection history.

The study authors said their research could have implications for the UK vaccination strategy, enabling the prioritisation of individuals who have never been infected previously by the virus.

Sixty-four individuals aged 22 to 63 years received at least one vaccine dose, with 24 given the Pfizer vaccine and 40 given the AstraZeneca.

Of those, 19 had previously been infected with Covid and they were vaccinated 6.25 months after infection.

To quantify antibody titres, up to 30 ml of blood was taken from volunteers.

The study, which was led by London-based Richmond Research Institute (RRI) and has not been peer reviewed, found that irrespective of which vaccine was used, those previously infected produced more antibodies overall and produced antibodies more rapidly.

Previously uninfected individuals’ geometric mean antibody titres were reached 25 days post-vaccination, compared with 16 days for those with prior infection.

Four weeks post-vaccination, those with previous infection had antibody titres 59-fold higher than those with no infection history, although the study aknowledges that it was not possible to calculate the precise level.

Those receiving the AstraZeneca vaccine appeared more likely to suffer side effects including chills, headache, and fever than those receiving the Pfizer drug. 

The researchers said it was interesting that one individual with no known history of Covid infection appeared to have antibody levels more consistent with a prior infection, suggesting they were unaware they had had the virus.

"In light of these findings, we suggest that a second vaccination for previously infected individuals may not be necessary in the short-term.

"It may be recommendable to prioritise individuals with no prior history of SARS-CoV-2 infection for a second vaccination, ahead of previously infected individuals who show a stronger response to their first inoculation."

"Conducting serology on people previously infected to confirm their high antibody titres will allow for a higher number of naïve people to be vaccinated in the short-term."

The study authors said further work is needed to examine the longevity of the immune response.