AZ shot wins UK nod — but efficacy questions linger

Dec. 30, 2020

The AstraZeneca/University of Oxford coronavirus vaccine has won an emergency approval in the UK. But British health regulators are skeptical of the company’s dosing claims.

According to the company, data published last month showed that when patients were given two full doses of the shot, its efficacy was about 62 percent. However, when patients received a half dose followed by a full dose, the efficacy shot up to 90 percent. AstraZeneca’s CEO recently said that the company had found a “winning formula” that would make it more competitive with its rivals on the market, Pfizer and Moderna, whose shots have been shown to be about 95 percent effective. The company is expected to release more data to support the higher efficacy claims. 

Yet, further investigation by Reuters showed that the discrepancy could be related to a potency miscalculation by Oxford researchers. The chair of a British advisory group also stated that the 90 percent claim did not hold up under further scrutiny — and that the difference in efficacy was instead linked to the duration of time between shots. The British official stated that a three month gap between doses rather than a one month gap could yield an 80 percent efficacy rate. 

Ultimately, the UK’s Medicines and Healthcare Products Regulatory Agency (MHRA) has recommended that patients wait 4-12 weeks in between doses. The MHRA is expected to release an assessment of the vaccine that will show the agency’s analysis of dosing data.

The UK has also approved Pfizer’s coronavirus vaccine, which is already being administered around the country.

Read the full Reuters report.