Huge studies this summer aim to prove which of several experimental COVID-19 vaccines are safe and effective. Moderna Inc. and Pfizer Inc.
began tests last week that eventually will include 30,000 volunteers each; in the next few months, equally large calls for volunteers will go out to test shots made by AstraZeneca, Johnson & Johnson and Novavax.
And some vaccines made in China are in smaller late-stage studies in other countries.AdvertisementFor all the promises of the U.S.
stockpiling millions of doses, the hard truth: Even if a vaccine is declared safe and effective by year's end, there won’t be enough for everyone who wants it right away -- especially as most potential vaccines require two doses.It’s a global dilemma.