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 a generalized optimization problem with a total of vaccine doses, that have to be optimally distributed between n different sub-populations, where sub-population u i represents people receiving the ith dose of the vaccine with efficacy α i . The particular case where n = 2 is solved first, followed by the general case of n dose regimen. Results: In the case of a two dose regimen, if the efficacy of the second dose is less than (or equal to) twice the efficacy of the first dose, the optimal strategy to maximize the number of effectively vaccinated people is to delay the second vaccine as much as possible. Otherwise, the optimal strategy would consist of administering the second dose as quickly as possible. In the general case, the optimal vaccination strategy would be to administer the k − th dose corresponding to the index providing the maximum inter-dose efficacy difference (α i − α i−1) for all possible values of i ∈ {1, … , n}, with α 0 = 0. 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.
Highlights
Since December 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has dramatically spread around the world leading to a heavy morbidity and mortality toll
The Food and Drug Administration (FDA) has so far authorized three COVID-19 vaccines for emergency use. Two of these are messenger RNA (mRNA) vaccines (PfizerBioNTech and Moderna). Both of these vaccines are approved based on a regimen of two doses, more recently a third booster dose has been recommended for high-risk persons in some developed countries after a variable duration
Due to the shortage in COVID-19 vaccine supplies, some countries have opted to delay the second dose of the COVID-19 vaccine for some period of time, aiming at getting the first dose of the vaccine in the arms of a large number of people, before proceeding with the second dose administration [5, 6]
Summary
Since December 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has dramatically spread around the world leading to a heavy morbidity and mortality toll. Janssen (Johnson & Johnson) was the third COVID-19 vaccine to receive emergency use authorization It consists on a single dose of the vaccine approved for individuals 18 years of age and older [3]. Due to the shortage in COVID-19 vaccine supplies, some countries have opted to delay the second dose of the COVID-19 vaccine for some period of time, aiming at getting the first dose of the vaccine in the arms of a large number of people, before proceeding with the second dose administration [5, 6] This strategy has sparked some heated debates world-wide for its pros and cons, and no clear consensus is reached among experts [7, 8]. Our model can be considered primarily for general population vaccination strategies and decision making
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