10-month gap between AstraZeneca vaccine doses effective, 3rd booster shot ups immunity: Study

The study by Oxford is likely to assist countries in their vaccine roll-out planning. Most nations have recommended a gap of 4 weeks to 12 weeks between AstraZeneca vaccines currently.

The human body's immune response to the AstraZeneca Plc Covid-19 vaccine is likely to be more effective if the gap between two doses is increased to about 10 months, a study by the University of Oxford published on Monday showed. Additionally, a third shot can push up the antibody levels, even more, said the study conducted on the vaccine now known as Vaxzevria.

A health worker shows a vial of the AstraZeneca Covid-19 vaccine against the coronavirus disease.(Reuters)

The study showed that an extended gap between the doses increased the level of protective antibodies. For the third shot, when given the first time after six months post the second dose, the booster was found to have induced a strong response and increased activity against coronavirus variants, the researchers found.

Governments around the world are faced with severe vaccine shortages amid a race to fully vaccinate their population against the infectious disease which has killed at least 3,925,816 people since the outbreak emerged in China in December 2019, according to the AFP.

At least 181,026,780 cases of coronavirus have been registered. The World Health Organization estimates that the pandemic's overall toll could be two to three times higher than official records, due to the excess mortality that is directly and indirectly linked to Covid-19.

In the last 24 hours, a total of 6,743 new deaths and 325,186 new cases were recorded worldwide.

The countries with the highest new deaths were India with 979 new deaths, followed by Brazil with 739 and Colombia with 664.

Some countries are also trying to tackle questions on booster shots in a bid to avoid overburdening the hospitals in the coming months of winter.

The study by Oxford is likely to assist countries in their vaccine roll-out planning. Most nations have recommended a gap of 4 weeks to 12 weeks between AstraZeneca vaccines currently.

Officials said this study will aid the world's response against the viral disease.

“This is about preparedness,” Andrew Pollard, lead investigator on the Oxford vaccine trials, said at a press briefing Monday.

"This data show we can boost responses giving another dose of the AstraZeneca-Oxford vaccine and that’s really important. More research on the duration of immunity from two doses and protection against variants would help determine whether booster doses are really needed," Pollard said.

What the study found

The study found that antibodies induced after a single dose survived to some extent after one year. Still, after 180 days the levels were half those seen at the 28-day peak. A second dose increased antibody levels between four- and 18-fold by one month after the shot, however.

Volunteers in the latest study were drawn from Oxford’s original early and late-stage trials for the vaccine last year. Thirty participants who only received a single dose in the trial were given a second one about 10 months after the first. An additional 90 participants from those studies received a third dose in March this year. All volunteers were between the ages of 18 and 55, reflecting the recruitment age at that stage of the trials last year.

More than half a billion doses of the Astra-Oxford vaccine have already been sent to 168 countries, according to the researchers.

(With inputs from Agencies)