When a safe and effective COVID-19 vaccine becomes available, it’s a complex process to distribute it and make it accessible to everyone who needs it.Distributing a vaccine will require scaling up manufacturing, logistically planning storage and prioritizing who gets it first, says Dr. William Moss, executive director of the International Vaccine Access Center at the Johns Hopkins University Bloomberg School of Public Health.The Centers for Disease Control and Prevention has contracted distribution to McKesson Corporation, a pharmaceutical company that distributes 150 million vaccine doses per year. McKesson will work with the CDC to distribute the vaccine across the U.S. to public health departments, hospitals, pharmacies and large health care organizations, he says.Another key part of distribution is maintaining what’s called the cold chain. Almost all vaccines need to stay cold, he says, and some newer ones such as Moderna’s messenger RNA vaccine may require even lower temperatures than usual.With concerns mounting about distribution to lower and middle-income countries in sub-Saharan Africa and Asia, it’s not yet clear how the process of administering a vaccine manufactured in the U.S. would work, he says. The Trump administration is cutting ties with the World Health Organization, specifically, a program called COVAX — a joint effort between the WHO, Gavi, The Vaccine Alliance, and the Coalition for Epidemic Preparedness and Innovation, to ensure equitable distribution on a global scale.“My own sense is that a vaccine manufactured in the United States will probably be prioritized for people within the United States,” Moss says. If a vaccine is manufactured outside the U.S., Moss predicts other countries will prioritize groups within their borders such as health care and essential workers and people at risk for the disease like the elderly. An ongoing conversation and plan are needed to ensure the vaccine gets to people who need it, he says.“There are efforts to try to avoid vaccine nationalism, where countries that develop a vaccine are using it only in their own country,” he says. “And it’s going to be a very tricky political decision to determine how vaccines will be allocated within the country and then shared more globally.”With people all over the world desperate for access to a vaccine, the race for one marks “an unprecedented situation,” he says. A few things set the COVID-19 vaccine apart from the most comparable past pandemic in recent history, the H1N1 influenza virus in 2009.Concerns about widespread transmission and mortality from H1N1 sparked the need for a global vaccine, he says, but the death toll and spread of the disease never reached the same level as COVID-19.And when H1N1 hit, both researchers and the public already had experience with influenza immunization, he says. With COVID-19, companies like Moderna are working with new types of vaccines such as the messenger RNA or another leading candidate called an adenovirus vector vaccine, where a gene from the spark protein of SARS-CoV-2 is inserted into an adenovirus and administered, he says.“Here, we’re trying to develop new vaccines to a new virus,” he says. “And some of the vaccine platforms or the way these vaccines are being manufactured is quite different than ways that we’ve done so in the past.”On top of working with multiple new types of vaccines from several different countries, a recent poll suggests only half of Americans plan to get a vaccine.Long-term immunity to the virus should protect people who receive the vaccine from those who refuse it, Moss says, but this is uncertain. The bar for “acceptable vaccine effectiveness” is as low as protecting half to 75% of the people who receive it, he says. Researchers also don’t know how long the vaccine will protect people, he says. An ideal vaccine would shield almost everyone who receives it for a long time, he says, “but if only half of those people are protected and that protection is short-lived, yes, then they would need to worry about those who do not get the vaccine” transmitting COVID-19 to others.As manufacturing capacity increases, the vaccine will become available to the general public — but this could take until mid to late 2021, Moss says.“There’s no doubt that early on there will not be sufficient quantity of vaccine doses to vaccinate everyone who wants to get vaccinated,” he says.