Third AstraZeneca jab 'effective against variants'

Third AstraZeneca jab 'effective against variants'

Vaxzevria, more commonly known as the AstraZeneca vaccine, is showing promising results in building strong immunity against Covid-19 for at least one year even after only one dose, according to the company.

AstraZeneca on Monday said a sub-analysis from the Oxford-led COV001 and COV002 trials with Vaxzevria induced strong immune responses following either a prolonged second dose interval of up to 45 weeks or following a third booster dose.

The results, published by the University of Oxford on the pre-print server of The Lancet, showed that antibody levels remain elevated from the baseline for at least one year following a single dose, the company said.

An extended interval between the first and second dose of Vaxzevria of up to 45 weeks resulted in up to an 18 fold increase in antibody response, measured 28 days after the second dose, it said.

With a 45-week interval between the first and second dose, antibody titres were four times higher than with a 12-week interval, showing that a longer dosing interval is not detrimental but can lead to stronger immunity, AstraZeneca said.

In addition, a third dose of the vaccine at least six months after a second dose, boosted antibody levels six fold and maintained T cell response, it said.

A third dose also resulted in higher neutralising activity against the Alpha, Beta and Delta variants, it said.

Both the late second dose and the third dose of Vaxzevria were reportedly less reactogenic than the first dose.

"This should come as reassuring news to countries with lower supplies of the vaccine, who may be concerned about delays in providing second doses to their populations," according to Sir Andrew J Pollard, chief investigator and director of the Oxford Vaccine Group at the University of Oxford.

"There is an excellent response to a second dose, even after a 10-month delay from the first," he said.

The analysis included volunteers aged 18 to 55 and had received either a single dose or two doses.

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