A COVID-19 vaccine that requires two doses may be more effective at protecting against the disease, but would also make the effort to immunize billions of people much more complicated, Bloomberg reported.
AstraZeneca, in partnership with the University of Oxford in England, and Moderna are planning to conduct final-stage testing of vaccines that would require two doses. Almost all standard vaccines are multiple-shot regimens, Tony Moody, MD, an immunologist at the Duke Human Vaccine Institute, told Bloomberg.
But the need for two doses would make manufacturing and logistics more complex.
"A one-shot vaccine would be ideal, but the first vaccines are highly unlikely to meet this very high threshold," Michael Kinch, PhD, a vaccine specialist and associate vice chancellor at Washington University in St. Louis, told Bloomberg. "As we hopefully move from whether there will be a vaccine to how to apply this, logistics are going to become the absolute most important topic."
Because a two-shot vaccine will be harder to distribute, it will likely disadvantage developing countries, Bloomberg reported. The challenges would multiply if the vaccine's efficacy wanes over time and repeat doses are needed, such as with the flu shot.
Merck has committed to only pursuing one-dose vaccines to simplify worldwide distribution, but its vaccine has yet to enter human trials.
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