Currently, the four most commonly administered vaccines in Viet Nam are Pfizer-BioNTech, Moderna, AstraZeneca, and Sinopharm. The interval between the two doses depends on the specific vaccine administered.
According to the recommendations of the US Centers for Disease Control and Prevention (CDC), the recommended interval between two doses is 3 weeks (21 days) for the Pfizer-BioNTech vaccine and 4 weeks (28 days) for the Moderna vaccine. However, this interval may be extended up to 6 weeks (42 days) if necessary [1].
Regarding the AstraZeneca vaccine, a study published in The Lancet in March 2021 reported an interval of 4 to 12 weeks between the first and second doses. Specifically, vaccine efficacy reached 81.3% among individuals who received the second dose 12 weeks or more after the first dose, whereas this efficacy decreased to 55.1% when the interval between the two doses was less than 6 weeks [2].
For the Sinopharm (Vero Cell) vaccine, the World Health Organization recommends an interval of 3 to 4 weeks between the first and second doses. If the administration of your second dose is delayed beyond 4 weeks, it should be administered as soon as possible [3].Across all four aforementioned vaccines, the interval between the two doses should not be shorter than the periods recommended by research studies.
We hope this information helps address your questions. We wish you good health, a prompt and complete vaccination course, and we look forward to Viet Nam overcoming the pandemic soon.
References:
[3] https://www.who.int/.../the-sinopharm-covid-19-vaccine...
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Source: https://www.facebook.com/reach.edu.vn