Did Astra Zenca save the developing world?
The AstraZeneca vaccine, developed in partnership with the University of Oxford, was one of the first vaccines available for use in the UK and around the world during the COVID pandemic.
More than two billion doses have been distributed to at least 170 countries, with around 50 million doses administered in the UK.
So despite being an excellent vaccine, the use of AstraZeneca in the UK has declined across the pandemic. It’s also not used much elsewhere in Europe, or in the US where it has yet to be approved.
The reason for its limited use in high-income countries could be a combination of two factors. First, it’s likely that the mRNA vaccines (specifically those manufactured by Pfizer and Moderna) are perceived to be even more effective than AstraZeneca. And second, the vaccine’s reputation took a hit when some people who received this vaccine subsequently developed blood clots.
On the first point, some research has indicated the mRNA vaccines offer slightly higher levels of protection against previously dominant variants, including delta. A 2022 study from the Netherlands that measured antibody levels against SARS-CoV-2 following vaccination showed Pfizer and Moderna performed better than the viral vector vaccines (including AstraZeneca). But one caveat here is that the participants who received the mRNA vaccines were much younger than the AstraZeneca recipients. Immune responses typically wane faster in older populations.
So why did AstraZenca perform well?
Among the reasons for a preference for AstraZeneca, there will be considerations around supply, cost and logistical issues. For example, the vaccine requires only regular refrigerator storage, compared with the mRNA vaccines which need to be frozen.
The UK and many other high-income countries are likely to continue predominantly using mRNA COVID vaccines. However, much of the knowledge we have around “which vaccine is better” relates to previous variants rather than omicron. As the virus continues to evolve, so must the evidence base.
There is an increasing body of evidence that “mixing and matching” vaccine types is safe and effective, and may even generate stronger or broader immune responses over time. In this light, there could be a role for AstraZeneca or other vaccines such as Novavax, alongside mRNA vaccines.
For many high-income countries in 2022, the mRNA vaccines are the vaccine of choice, rather than AstraZeneca. The mRNA vaccines are also being manufactured in sufficiently large volumes to make supply much less of an issue than it was earlier in the pandemic. These are all important factors for national decision-makers. However, it’s important to emphasise that the AstraZeneca vaccine is a safe and effective product, and remains a vital tool to underpin the global response to the pandemic.