Coronavirus: Why AstraZeneca is not the go-to COVID-19 vaccine for many international countries

Over a year has passed by since COVISHIELD vaccine, developed by the pharma giant AstraZeneca inc. and Oxford University, was launched in India. While the vaccine initially thrived in the international market, due to a controversial development, it was suspended for use by more that a dozen countries including Denmark, Germany and France.

Additionally, even though a few countries, including India and the United Kingdom, continue to administer the vaccine in question, health professors have shared why it is less likely to be used as booster shots in several countries.

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That said, let us revisit how it all started and why AstraZeneca is not the go-to COVID vaccine for many international countries.

It all started in March, 2021, when Denmark became the first country to stop the use of the AstraZeneca COVID vaccine. Following reports of blood clots in some people, Danish health authorities halted the administration of the vaccine and said, "at present, it cannot be concluded whether there is a link between the vaccine and the blood clots."

However, countries such as Ireland, Norway, Bulgaria, Thailand and Congo followed suit and suspended the use of the vaccine. Patients were admitted to the hospital for bleeding, blood clots and low platelet count.

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The World Health Organisation (WHO) and the European Medicines Agency (EMA) have jointly said that there is no link between the vaccine and the blood clots.

“In extensive vaccination campaigns, it is routine for countries to signal potential adverse events following immunization. This does not necessarily mean that these events are linked to vaccination. But, it’s routine practice to investigate them — it shows that the surveillance system works and that effective controls are in place,” says the global health agency.

Initially, when several people were being inoculated at one time, problems and reports of adverse effects were expected to arise, given that large groups of people were being vaccinated, says experts.

However, experts are still reviewing and investigating the date for conclusive reports.

Although countries like India and the United Kingdom are still offering AstraZeneca vaccine for first and second jabs, since we have moved a step ahead and booster shots have come into play, health professors explain why the vaccine is less likely to be used as a booster jab.

Based on research, Professor Linda Bauld from Edinburgh University says that administering AstraZeneca vaccine as a booster is no longer the "most effective" way to immunise people against the SARs-COV-2 virus.

Citing the study, she says, “The CovBoost study showed mRNA vaccines were particularly valuable for the booster."

“And that means Pfizer and Moderna have been used for the initial booster and now for the additional pone that's being rolled out.

“When that's either on top of the first vaccines, it looks to be the most effective approach," she adds.

However, she also mentions that people who have certain allergies to the ingredients of the mRNA vaccines can continue to get themselves jabbed by the AstraZeneca vaccine, which uses a harmless animal virus (a viral vector) to trigger immune response.

Denmark was the first country to suspend COVID-19 Vaccine AstraZeneca, followed by Ireland, Thailand, the Netherlands, Norway, Iceland, Congo, and Bulgaria.

European countries, including Germany, France, Italy, and Spain have stopped the use of AstraZeneca's COVID vaccine.

Sweden, Latvia and Slovenia joined the league in banning the use of the vaccine.

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AstraZeneca COVID vaccine a.k.a. COVISHIELD, manufactured by the Serum Institute of India, is one of the vaccines authorised for use in the country, besides COVAXIN and Sputnik V.

COVISHIELD is made from a weakened version of chimpanzee adenovirus vector, modified to look more like coronavirus so as to trigger a strong immune response.

While no vaccine is 100% effective, the rate of efficacy against severe infection was found to be 80% with two doses of Covishield as against 69% with two doses of Covaxin, as per an ICMR study.

Reports suggest that currently, Serum Institute-manufactured COVISHIELD accounts for over 50% of the vaccine doses given in the country. Furthermore, India is also considering the use of COVISHIELD as a suitable booster shot, even though research suggests otherwise.

Mix and match of COVID vaccines has been seen as another technique to increase vaccine effectiveness. Scientists have been expanding the horizon and looking into the possibility of mixing vaccines, so as to explore the chances of increased efficacy.

A UK-based Lancet study found that mixing doses of AstraZeneca vaccine with an mRNA vaccine produced a more robust immune response against the COVID-19 than the two doses of AstraZeneca.

In several European countries, this technique has been used and is said to prove effective. However, India is yet to explore this method.