Story at a glance
- The Pfizer-BioNTech vaccine’s second dose is recommended within 21 days of the first dose.
- The Moderna vaccine’s second dose should be given within 28 days.
- In the U.S., distribution of vaccine doses is slowing down vaccination efforts.
While more than 14 million doses of coronavirus vaccines have been distributed so far in the U.S., only about 4 million first doses have been administered, according to the Centers for Disease Control and Prevention (CDC). Some health experts in the U.K. have recommended delaying second doses so that more people get their first doses sooner. Health experts in the U.S. disagree with that approach, saying it strays from what we understand from the vaccines’ clinical trials.
The U.K.’s Joint Committee on Vaccination and Immunisation recommends that the government prioritize getting first doses out to as many people in the at-risk populations as possible.
“Everyone will still receive their second dose and this will be within 12 weeks of their first,” states the U.K. government in a press release. “The second dose completes the course and is important for longer term protection.”
This suggests that people will get their second doses, just that a slight tweak in current priorities for appointments should go to those who have not yet had their first dose.
In the U.S., it seems the issue is somewhat different. Distribution seems to be the bottleneck and not necessarily the number of doses at this point. People are struggling to get appointments or are lining up for the vaccine and getting turned away.
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“We have an issue with distribution, not the number of doses,” says vaccine expert Saad Omer at Yale University to The New York Times. “Doubling the number of doses doesn’t double your capacity to give doses.”
To be clear, the number of doses is not increasing or decreasing, but scientists are debating if second doses for vaccines that require an additional shot should be delayed so that more people can get their first doses.
Some health officials in the U.S. have said they would be against prioritizing giving out more first doses. “I would not be in favor of that,” says Anthony S. Fauci, the nation’s top infectious diseases expert, to CNN’s Elizabeth Cohen according to the Times. “We’re going to keep doing what we’re doing.”
The U.K. says people would get their second dose within 12 weeks of their first, but for the Pfizer-BioNTech and Moderna vaccines, the second dose should be given by three and four weeks, respectively. Although the CDC notes “there is no maximum interval between the first and second dose for either vaccine,” and stretching that period to 12 weeks would mean that health officials are doing something that the clinical trials did not account for, so we would be in unknown territory in terms of efficacy.
“The problem, though, is that’s not how the studies were conducted,” says emergency physician Leana Wen to CNN. “The key is to follow the science. We don’t know what happens, how long the immunity lasts.”
For up-to-date information about COVID-19, check the websites of the Centers for Disease Control and Prevention and the World Health Organization. For updated global case counts, check this page maintained by Johns Hopkins University or the COVID Tracking Project.
You can follow Chia-Yi Hou on Twitter.
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