The dosing schedule may impact the level and durability of immunity.
Title: Higher serological responses and increased vaccine effectiveness demonstrate the value of extended vaccine schedules in combatting COVID-19 in England (2021-07-28)
At 2-5wks after dose 2, geometric mean titres (GMTs) found to be about 9 times higher for 9-12wk interval compared to normal 3-4wk interval with BioNTech (Pfizer/BNT162b2).
"Our findings support the UK approach of prioritising the first dose of COVID-19 vaccines, with evidence of higher protection following extended schedules. Given global vaccine constraints, these results are relevant to policymakers, especially with highly transmissible variants and rising incidence in many countries."