Although a “knock-out blow” vaccine would be ideal, early vaccines may carry limitations, said Robin Shattock, an Imperial College London professor leading development of an experimental shot, according to Bloomberg.
“Is that protection against infection?” Shattock told the news company. “Is it protection against illness? Is it protection against severe disease? It’s quite possible a vaccine that only protects against severe disease would be very useful.”
A vaccine showing an impact on disease, but not infection, could be used, the outlet wrote.
“Vaccines need to protect against disease, not necessarily infection,” said Dennis Burton, an immunologist and vaccine researcher at Scripps Research in La Jolla, California.
Such a vaccine may lead to complacency in areas fatigued from lockdowns, one drug development expert warned.
“My guess would be that the day after someone gets immunized, they’re going to think, ‘I can go back to normal. Everything will be fine,’” said Michael Kinch, associate vice chancellor at Washington University in St. Louis. “They’re not going to necessarily realize that they might still be susceptible to infection.”
The outlet noted that few, if any, vaccines are 100 percent effective in all recipients. The World Health Organization (WHO) on June 9 listed 136 vaccine candidates, 10 of which were categorized under clinical evaluation.
According to Michael Felberbaum, a spokesman for the Food and Drug Administration, the agency would potentially consider an indication related to prevention of severe disease, if data supported benefits of vaccination. For licensure, a vaccine would not be required to protect against infection, he said.
In a June 11 update from Moderna, Inc. for example, the company said its late-stage trial’s primary endpoint is the prevention of symptomatic COVID-19 disease; key secondary endpoints include prevention of infection and severe COVID-19 disease.
According to Kinch, “there will never be a truly perfect vaccine,” however follow-ups on imperfect yet practical vaccines are a possibility.