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Wednesday December 8th, 2021

COVID-19 vaccine mix-and-match can exceed performance of NMRA vaccines: Nature

ECONOMYNEXT – Mixing and matching Covid 19 vaccines is highly effective at preventing the disease and can exceed the performance of the standard mRNA vaccines, international studies show.

British scientific journal Nature reported on Friday (21) that several studies around the world has shown that ‘mix and match’ regimens are highly effective at preventing COVID-19, roughly matching or even exceeding the performance of mRNA vaccines.

The high antibody levels and other strong immune responses elicited by mix-and-match regimens suggested they would offer good protection against disease.

Nature reported that the studies sprang out of a natural experiment that began in March, when a number of countries partially or completely halted the use of the vaccine developed by the University of Oxford and the pharmaceutical company AstraZeneca in Cambridge, UK, because of extremely rare but serious side effects.

“This meant that some people who’d already received one dose of this vaccine then had a different vaccine as their second jab,” Nature said.

“I was delighted to see that it’s as effective as one would expect. This is really good news and this will certainly have influence on clinical practice,” the journal quoted Immunologist Martina Sester at the aarland University in Homburg, Germany, as saying.

Nature quoting Matthew Snape, a vaccinologist at the University of Oxford, UK, said these emerging effectiveness data support the use of these approved COVID-19 vaccines in either the standard or mixed schedules.

The studies were done in Sweden, Denmark and France looking at various populations at various times, including during the rise of the hyper-infectious Delta variant. All three studies have agreed that mix-and-match, or heterologous, vaccination is highly protective.

In Sweden, health authorities had severely curtailed the use of the Oxford-AstraZeneca vaccine which relies on a weakened chimpanzee cold virus.  Over 100,000 people in Sweden received a dose of AstraZeneca, followed by an mRNA-based jab, either the vaccine from Moderna in Cambridge, Massachusetts, or the one developed by pharmaceutical company Pfizer, based in New York City, and biotechnology firm BioNTech in Mainz, Germany.

After analyzing the data, scientists at Umeå University in Sweden found that compared with unvaccinated people, those on a mixed vaccination schedule were 68 percent less likely to develop a symptomatic infection, whereas the 430,000 people who received two doses of AstraZeneca were 50 percent less likely to do so.

“These and other figures make it clear that the heterologous regimens are more effective than two doses of AstraZenec,” scientists at Umeå University in Sweden has said.

According to Nature, another study in Denmark which has not been peer reviewed yet has found that one dose of AstraZeneca followed by one dose of Pfizer-BioNTech was 88 percent effective at preventing SARS-CoV-2 infection and has an effectiveness similar to that of two doses of Pfizer.

However, a study in France has shown that SARS-CoV-2 infection rates in the mix-and-match group were half that of the group that received two doses of Pfizer. The scientist at Inserm and the University of Lyon in France showed these results after analyzing data from 2,512 health-care workers who received a combination of AstraZeneca and Pfizer vaccines, and more than 10,000 who received two doses of the latter.

Scientists says mix-and-match COVID-19 vaccines might have passed the effectiveness test but questions remain, such as how well the mix-and-match vaccines will hold up over time, and whether and when they need boosting with extra doses.

Nature reported that unpublished data from Umeå University in Sweden has found that the durability of the protection conferred by mixed vaccinations is comparable with that of mRNA vaccines. However, the data also hint that higher-risk individuals would benefit from a third dose.

Scientists say mixing and matching vaccines could protect organ-transplant recipients and others with weakened immune systems better than the standard vaccine regimen.

Upon analysing data of the studies, Sri Lanka on Friday (22) decided the booster dose program will start from first week of November.

Army Commander Gen Shavendra Silva, who also heads the national COVID-19 task force on Friday told reporters that the Pfizer-BioNTech COVID-19 vaccine will be administered as a booster dose for frontline workers in the health, military, police personnel, and tourism sectors starting November 01. (Colombo/Oct22/2021)


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