AUTHOR=Berkane Soulaimane , Harizi Intissar , Tayebi Abdelhamid , Silverman Michael S. , Stranges Saverio 

TITLE=Should We Delay the Second COVID-19 Vaccine Dose in Order to Optimize Rollout? A Mathematical Perspective

JOURNAL=International Journal of Public Health

VOLUME=Volume 66 - 2021

YEAR=2022

URL=https://www.ssph-journal.org/journals/international-journal-of-public-health/articles/10.3389/ijph.2021.1604312

DOI=10.3389/ijph.2021.1604312

ISSN=1661-8564

ABSTRACT=Objectives: With vaccination shortage persisting in many countries, adopting an optimal vaccination program is of crucial importance. Given the slow pace of vaccination campaigns globally, a very relevant and burning public health question is whether it is better to delay the second COVID-19 vaccine shot until all priority group people have received at least one shot. Currently, many countries are looking to administer a third dose (booster shot), which raises the question of how to distribute the available daily doses to maximize the effectively vaccinated population. 
Methods: We formulate an optimization problem with a total of n vaccine doses, that have to be optimally distributed between n different sub-populations, where  the i-th dose of the vaccine has an efficacy alpha_i. 
Results: The optimal vaccination strategy would be to administer the k-th dose corresponding to the maximum inter-dose efficacy difference.
Conclusion: Our results suggest that although extending the interval between doses beyond 12 weeks was likely optimal earlier in the pandemic, the reduced single dose efficacy of vaccines against the delta variant make this approach no longer viable.