Some good hilites on sterilizing immunity from:https://www.statnews.com/2020/05/22/the-....
Ideally, vaccines would prevent infection entirely, inducing whats known as sterilizing immunity. But early work on some of the vaccine candidates suggests they may not stop infection in the upper respiratory tract and they may not stop an infected person from spreading virus by coughing or speaking.
Michael Mina, an infectious diseases epidemiologist at Harvards T.H. Chan School of Public Health, thinks achieving sterilizing immunity with a vaccine will not be possible for Covid-19. Experience with human coronaviruses and with multiple pathogens that cause colds shows immunity that develops after infection with respiratory tract infections is not lifelong. In some cases, the duration is measured in months, not years.
Munster agreed trying to develop vaccines that confer sterilizing immunity would be a heavy lift with this coronavirus. I think we really need to focus on what are the fastest achievable true public health goals of the vaccine, which is protecting the vulnerable people and protecting health care workers as well, he said.
Earlier this week Moderna, the Cambridge, Mass.-based biotech, said eight people in a Phase 1 trial of its Covid-19 vaccine developed neutralizing antibodies to the virus.
Neutralizing antibodies should protect against severe Covid-19 disease, Kanta Subbarao, a vaccine expert who is director of the World Health Organizations influenza collaborating center in Melbourne, Australia, recently wrote in a commentary in the journal Cell Host and Microbe.
But Subbarao told STAT she wouldnt be surprised if neutralizing antibodies dont protect against infection in the upper airways. Like Munster, she doesnt think thats reason not to pursue these vaccines.
Some experts hope that even if the vaccines dont prevent infection in the upper airways, they may reduce the amount of virus a vaccinated person generates and emits.
Hopefully it would diminish although we dont know this the levels of replication on the mucosal surfaces, said Mark Feinberg, CEO of the International AIDS Vaccine Initiative, which is working to develop an orally administered Covid-19 vaccine. That route of administration may improve the vaccines capacity to protect the mucus membranes of the upper airways.
Mina sees a potential upside to Covid-19 vaccines that dont stop infection and transmission, saying low-level circulation of the virus could act as a natural booster to keep peoples immunity levels high.
Its a little bit sobering to see that, while we may get protection against disease [and] protect people from getting sick, we may not get nearly as effective protection against transmission, Fortune said during a briefing Thursday for reporters. Which means that to protect the population, were going to have to be vaccinating many, many more people, because we cant rely on getting to a lot of people and having the epidemic die out through herd effects.