Delaying the second dose of the Pfizer/BioNTech vaccine against COVID-19 beyond the recommended three-week interval used in clinical trials seems to evoke a stronger antibody response in the elderly, noted UK researchers. 

Shortly after the vaccine became available, UK health officials had advised to administer the second dose 12 weeks after the first one in order to allow more people to get a first dose early on. A new paper expected to appear on medRxiv noted that among 175 individuals, 80 to 99 years of age, those who got their second vaccine dose at 12 weeks had antibody responses 3.5 fold higher than those who got the dose after three weeks. The peak T cell responses were found to be higher in those with a 3-week dose interval… (Reuters, May 15, 2021)