EMA recommends proceeding with second dose of AstraZeneca Covid-19 vaccine

The European Medicines Agency (EMA) human medicines committee (CHMP) has recommended to proceed with giving a second dose of Vaxzevria, the brand name of the AstraZeneca vaccine against Covid-19, between four and 12 weeks after giving the first one in line with the product information, the EMA said in a statement on April 23.

The CHMP considered recommendations to give the second dose of Vaxzevria after a longer interval than the recommended 4-12 weeks, to not give a second dose at all, or to give an mRNA vaccine as a second dose.

“However, there has not been enough exposure and follow-up time to determine whether the risk of blood clots with low blood platelets after a second dose will differ from the risk after the first dose. At present there are no or limited data to change current recommendations,” the EMA said.

“The benefits of Vaxzevria outweigh its risks in adults of all age groups; however, very rare cases of blood clots with low blood platelets1 have occurred following vaccination.”

To support national authorities making decisions on how to best use the vaccine in their territories, CHMP had further analysed available data to put the risk of these very rare blood clots in the context of the vaccine’s benefits for different age groups and different rates of infection, the EMA said.

The analysis will inform national decisions on the roll out of the vaccine, taking into account the pandemic situation as it evolves and other factors, such as vaccine availability. The analysis could change as new data become available.

Vaxzevria is effective at preventing hospitalisations, intensive care unit (ICU) admissions and deaths due to Covid-19. The most common side effects are usually mild or moderate and get better within a few days, the agency said.

The most serious side effects are very rare cases of unusual blood clots with low blood platelets, which are estimated to occur in one in 100 000 vaccinated people. People should seek medical assistance if they have symptoms, the EMA said.

The committee analysed the vaccine’s benefits and the risk of unusual blood clots with low platelets in different age groups in the context of the monthly infection rates: low (55 per 100 000 people), medium (401 per 100 000 people) and high (886 per 100 000 people).

The analysis looked at prevention of hospitalisations, ICU admissions and deaths due to Covid-19, based on different assumptions of vaccine effectiveness to contextualise the occurrence of these unusual blood clots. It showed that the benefits of vaccination increase with increasing age and infection rates.

There were insufficient data available from across the EU to provide further context on benefits and risks with regard to sex.

“The current analysis does not constitute an assessment of the vaccine’s benefit-risk balance, which remains positive for adults in all age groups,” the EMA said.

“As for all vaccines, Vaxzevria is approved in the EU because its benefits outweigh the risks for an individual potentially exposed to the agent causing disease.”

However, national authorities later consider other factors when deciding how to best use the vaccines, the EMA said.

Because vaccination is a public health intervention, national authorities could also consider the benefits to the population as a whole, as vaccines may protect more people than are vaccinated.  

“While this analysis may be subject to change as new data become available, it may guide EU member states when they adjust their vaccination strategies depending on the infection rates and ages of people who still need to be vaccinated,” the EMA said.

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