New findings about a potential COVID-19 vaccine from the University of Oxford and AstraZeneca indicate that it is roughly 70% safe and effective, but questions remain about how well it will protect people over the age of 55 – a major vaccine concern that health officials hope Reliance on it worldwide due to its low cost, availability and ease of use.

However, experts say the vaccine appears likely to be approved, despite some confusion over results and lower levels of protection than other vaccine candidates have shown.

“What we can see sounds plausible, but it’s a little more complex than we’ve seen so far,” said Dr. Paddy Krish, a researcher at Vanderbilt University who is helping to test two other vaccines. “If this had been the first report released, the field would still be excited to get a vaccine.”

It’s difficult to explain because something wrongly led some participants to getting half a dose followed by a full dose instead of two full doses as intended.

The researchers claim that the vaccine protected against disease in 62% of those given two full doses and 90% of those who gave half the dose initially. However, independent experts said the second group was too small – 2,741 people – to judge the potential value of the approach and that more testing was needed.

The half-dose group also did not include anyone over the age of 55, and among others in the study, only about 20% were in that age group.

It is unclear whether the results will be enough to lead regulators in the UK and elsewhere to agree to their use immediately.

“We have no safety concerns about the vaccine,” said one of the study leaders, Andrew Pollard of Oxford, with no hospitalization or severe illness among those who received it, and results from all study sites consistently show benefit.

He said: “The only way we can have the epidemic behind us is if we get doses of the vaccine there.”

AstraZeneca’s Maine Pangalos described the results as “very convincing” and said they “clearly show that we have an effective vaccine” that meets approval standards around the world. “I really think this vaccine will have a big impact on the epidemic,” he said.