My Auntie got her 1st dose of Pfizer vaccine today. When I scheduled her at the Pharmacy, they asked to schedule for 2nd dose - about 4 weeks later. Another Auntie (out of state) got 1st dose of Moderna vaccine, but was unable to get 2nd dose due to snow delays. She said she can wait up to 6 weeks for 2nd dose. I am searching Google for OPTIMAL timings between 1st and 2nd dose of covid vaccine based on science, not based on vaccine shortages. According to below article, 2nd Dose of Pfizer can be taken after 21 days. Why did the Pharmacy ask me to select a day 4 weeks from now for 2nd dose??? This whole thing is very confusing. Please share your experiences and medical knowledge (I believe we have MDs on IL) CDC: Gap Between Vaccine Doses Could Be 6 Weeks "If the second dose can’t be scheduled in the recommended time frame -- 21 days after the first dose for Pfizer and 28 days for Moderna -- people can wait up to 6 weeks, the CDC said in an update published Thursday."