The World Health Organization's Strategic Advisory Group of Experts on immunization said the interval between doses of Pfizer-BioNTech's COVID-19 vaccine can be extended up to 42 days in countries with severe supply constraints, according to interim guidance published Jan. 8
The ideal interval between doses is 21 to 28 days, though in countries that "face exceptional circumstances of vaccine supply constraints combined with a high disease burden," the second dose may be delayed up to six weeks. The recommendation was based on available clinical trial data.
This strategy should be used as a "pragmatic approach" to increase the number of people benefiting from the first dose until the vaccine is more widely available, the report said. If extending the interval, countries should ensure people still have access to the second dose, WHO experts said, adding that it will update the recommendation if more data on extending interval doses becomes available.
Earlier this week, the FDA issued a statement warning against reducing the number of doses, extending the length of time between doses, altering the dose amount, or mixing and matching vaccines.
"At this time, suggesting changes to the FDA-authorized dosing or schedules of these vaccines is premature and not rooted solidly in the available evidence," the FDA wrote. "Without appropriate data supporting these changes … we run a significant risk of placing public health at risk, undermining the historic vaccination efforts to protect the population from COVID-19."
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