Studies provide glimpse at efficacy of Covid-19 vaccines from Oxford-AstraZeneca and CanSino

New data offer glimpse of efficacy of Oxford-AstraZeneca Covid-19 vaccine The vaccine generated an immune response in a study of roughly 1,000 patients, and all of the side effects were deemed mild or moderate. Matthew Herper STAT

A Covid-19 vaccine being developed by Oxford University and the drug giant AstraZeneca generated an immune response in a study of roughly 1,000 patients, according to interim results published Monday.

The data, published in the medical journal the Lancet, also show that the vaccine caused side effects, including fever, headaches, muscle aches, and injection site reactions, in about 60% of patients. All of the side effects were deemed mild or moderate, and all resolved themselves over the course of the study.

While the Oxford-AstraZeneca vaccine, known as AZD1222, has moved most rapidly into larger-scale studies of any major contender — and AstraZeneca has said that billions of doses could be manufactured — the new data represent the first glimpse researchers have gotten at its efficacy. They show a relatively safe vaccine, though side effects were greater than for a meningitis vaccine, to which it was compared, that engages the immune system to fight the virus.

The Lancet also published results of another vaccine, from the Chinese biotech CanSino, that had been previously released. The Phase 2 results showed that, as was seen in the Phase 1 data, the vaccine induced neutralizing antibody responses — which could be vital to preventing the disease’s dangerous symptoms — in most subject. But further study continues to show that this vaccine works better in some people than others. And among those it didn’t work as well in were people aged 55 and older, a key target for Covid-19 vaccination.

“The results of both studies augur well for phase 3 trials, where the vaccines must be tested on much larger populations of participants to assess their efficacy and safety,” wrote two vaccine researchers from Johns Hopkins University, Naor Bar-Zeev and William Moss, in an accompanying editorial.

The data on the Oxford-AstraZeneca vaccine do not provide enough information to predict whether it will be more effective than other vaccines that are also entering clinical trials.