AstraZeneca nears temporary OK for COVID-19 vaccine, plots extra trial

Pascal Soriot
AstraZeneca CEO Pascal Soriot (AstraZeneca)

The U.K. government has asked the national regulator to consider clearing AstraZeneca’s COVID-19 vaccine for temporary supply as soon as it receives safety, quality and efficacy data. Requesting use of the fast track positions the U.K. to be among the first countries to begin a COVID-19 vaccination campaign. 

Officials at the U.K. Medicines and Healthcare products Regulatory Agency (MHRA) have already begun assessing some of the data on the viral vector vaccine, AZD1222, under a rolling review scheme. However, typically the MHRA would wait until conducting a full review of the late-phase data, which AstraZeneca shared a glimpse of last week, before authorizing the vaccine for use in the U.K. 

The temporary supply of the vaccine would position the rollout to start before the MHRA completes its review of the full data set. Under pressure to bring COVID-19 cases down without further harming the economy, the U.K. government has formally asked the MHRA to assess whether AZD1222 is suitable for temporary supply.

If the MHRA deems the vaccine suitable for the scheme, the U.K. could begin vaccinating high-risk individuals as soon as AstraZeneca “submits the necessary safety, quality and efficacy data.” The U.K., which expects to receive 4 million doses by the end of the year, currently plans to prioritize residents and staff at care homes, reflecting the number of deaths at such facilities so far in the pandemic. 

In its release to disclose the request to the MHRA, the U.K. government referenced the divergent efficacy results associated with the two vaccine regimens included in the late-phase data analysis but made no comment about which will be cleared for use. 

The mistakenly delivered half-dose regimen appears to be more effective but was only given to ‌2,741‌ ‌subjects. Given the size of the group, differences between the demographics of the half- and full-dose cohorts and the lack of an accepted mechanistic explanation for the better efficacy, it is possible the 90% figure is an anomaly that will fail to stand up to a more rigorous assessment of the regimen.

AstraZeneca is gearing up to generate more data on the half-dose regimen. CEO Pascal Soriot told Bloomberg AstraZeneca plans to run an additional global clinical trial, rather than add an arm to its existing U.S. study, to validate whether the half-dose regimen is more efficacious. The new trial “could be faster, because we know the efficacy is high so we need a smaller number of patients,” Soriot said.  

The late-phase data AstraZeneca plans to use to win authorization in the U.K. and the rest of Europe cover 11,636 people. Moderna and Pfizer enrolled at least 30,000 people in the phase 3 trials of their COVID-19 vaccines. AstraZeneca is running a 40,000-subject phase 3 at sites in the U.S. and a few South American countries but began enrollment after Moderna and Pfizer and was held up by the FDA’s response to a suspected unexpected serious adverse reaction in the U.K. study. 

It is unclear whether the FDA would authorize a COVID-19 vaccine based on overseas data, but the nature of the AZD1222 data has made the situation facing AstraZeneca less ambiguous. “With those results, it’s more likely that we will need the U.S. data,” Soriot said.