Potential benefits of delaying the second mRNA COVID-19 vaccine dose

Abstract

Vaccination against COVID-19 with the recently approved mRNA vaccines BNT162b2 (BioNTech/Pfizer) and mRNA-1273 (Moderna) is currently underway in a large number of countries. However, high incidence rates and rapidly spreading SARS-CoV-2 variants are concerning. In combination with acute supply deficits in Europe in early 2021, the question arises of whether stretching the vaccine, for instance by delaying the second dose, can make a significant contribution to preventing deaths, despite associated risks such as lower vaccine efficacy, the potential emergence of escape mutants, enhancement, waning immunity, reduced social acceptance of off-label vaccination, and liability shifts. A quantitative epidemiological assessment of risks and benefits of non-standard vaccination protocols remains elusive. To clarify the situation and to provide a quantitative epidemiological foundation we develop a stochastic epidemiological model that integrates specific vaccine rollout protocols into a risk-group structured infectious disease dynamical model. Using the situation and conditions in Germany as a reference system, we show that delaying the second vaccine dose is expected to prevent COVID-19 deaths in the four to five digit range, should the incidence resurge in the first six months of 2021. We show that this considerable public health benefit relies on the fact that both mRNA vaccines provide substantial protection against severe COVID-19 and death beginning 12 to 14 days after the first dose. The model predicts that the benefits of protocol change are attenuated should vaccine compliance decrease substantially. To quantify the impact of protocol change on vaccination adherence we performed a large-scale online survey. We find that, in Germany, changing vaccination protocols may lead only to small reductions in vaccination intention depending on liability issues associated with postponing the second dose. In sum, we therefore expect the benefits of a strategy change to remain substantial and stable.

Optimal vaccine roll-out strategies including social distancing for pandemics

“…Remarkably, a similar result has been obtained from the analysis of (Maier et al, 2021;Silva et al, 2021) using detailed models of differential equations. In (Maier et al, 2021) the authors showed that delaying the second vaccine dose is expected to prevent COVID-19 deaths in a four to five-digit range. However, their analysis does not consider social distancing measures as the present study.…”

“…The availability of vaccines against SARS-CoV-2 allowed new possibilities to control the pandemic and aspired to develop effective protection against the virus transmission. By the end of 2020, a variety of vaccines were introduced with different immunization efficacies (Maier et al, 2021;Das et al, 2021). The vaccination process varied widely among countries, with different vaccination rates per day over the entire population without a common protocol (Maier et al, 2021;Israel.gov.health, 2021;Robert.Koch.Institute, 2021;greece.gov, 2021).…”

“…By the end of 2020, a variety of vaccines were introduced with different immunization efficacies (Maier et al, 2021;Das et al, 2021). The vaccination process varied widely among countries, with different vaccination rates per day over the entire population without a common protocol (Maier et al, 2021;Israel.gov.health, 2021;Robert.Koch.Institute, 2021;greece.gov, 2021). Until November 29, 2021, more than 264 million infections with 5.26 million deaths have been reported worldwide, while more than nine billion doses have been vaccinated (WHO, 2021).…”

Effects of infection fatality ratio and social contact matrices on vaccine prioritization strategies

“…All vaccines approved for emergency use have a high potential to prevent severe cases after complete vaccination and immunization whose time depend on the type of vaccine. CoronaVac, Pfizer-BioNTech, and Vaxzevria demand at least two shots with different intervals (21 to 90 days) for maximum protection [31,32] while a late third dose has been currently recommended, especially for the most vulnerable groups that present weak antibody responses [33][34][35]. However, as usual for anti-viral vaccines, the capacity of COVID-19 vaccines to impede infections and mild symptoms is lower than their efficiency to reduce death and severe cases [20,21,[23][24][25].…”