Two scientists have won the Nobel Prize in physiology or medicine for their discovery of microRNA, tiny bits of genetic material that serve as on and off switches inside cells that help control what the cells do and when they do it.

Two scientists have won the Nobel Prize in medicine for discoveries that enabled the creation of mRNA vaccines against COVID-19 and that could be used to develop other shots in the future.

FILE - In this Friday, Jan. 22, 2021 file photo, empty vials of the Pfizer-BioNTech COVID-19 vaccine are seen at a vaccination center at the University of Nevada, Las Vegas in Las Vegas. (AP Photo/John Locher)With demand for COVID-19 vaccines outpacing the world’s supplies, a frustrated public and policymakers want to know: How can we get more? Makers of COVID-19 vaccines need everything to go right as they scale up production to hundreds of millions of doses — and any little hiccup could cause a delay. “It’s just not that easy.”DIFFERENT VACCINES, DIFFERENT RECIPESThe multiple types of COVID-19 vaccines being used in different countries all train the body to recognize the new coronavirus, mostly the spike protein that coats it. But possibly the easiest way to get more doses is if other vaccines in the pipeline are proven to work.

Many scientists dont expect a coronavirus vaccine to be nearly as protective as the measles shot. If the best COVID-19 vaccine is only 50% effective, "thats still to me a great vaccine, said Dr. Drew Weissman of the University of Pennsylvania. About 15 experimental COVID-19 vaccines are in various stages of human studies worldwide. Nothing is going to be easy.The Oxford shot, with a 10,000-person study underway in England, already encountered that hurdle. EXPECT IMPERFECT PROTECTIONAnimal research suggests COVID-19 vaccines could prevent serious disease but may not completely block infection.