Discussion paper

DP16599 Testing fractional doses of COVID-19 vaccines

Due to the enormous economic, health, and social costs of the COVID-19 pandemic, there are high
expected social returns to investing in parallel in multiple approaches to accelerating vaccination. We
argue there are high expected social returns to investigating the scope for lowering the dosage of some
COVID-19 vaccines. While existing evidence is not dispositive, available clinical data on the
immunogenicity of lower doses combined with evidence of a high correlation between neutralizing
antibody response and vaccine efficacy suggests that half- or even quarter-doses of some vaccines could
generate high levels of protection, particularly against severe disease and death, while potentially
expanding supply by 450 million to 1.55 billion doses per month, based on supply projections for 2021. An
epidemiological model suggests that even if fractional doses are less effective than standard doses,
vaccinating more people faster could substantially reduce total infections and deaths. The costs of further
testing alternative doses are much lower than the expected public health and economic benefits.
However, commercial incentives to generate evidence on fractional dosing are weak, suggesting that
testing may not occur without public investment. Governments could support either experimental or
observational evaluations of fractional dosing, for either primary or booster shots. Discussions with
researchers and government officials in multiple countries where vaccines are scarce suggest strong
interest in these approaches.


Więcek, W, A Ahuja, E Chaudhuri, M Kremer, A Simoes Gomes Junior, C Snyder, A Tabarrok and B Tan (2021), ‘DP16599 Testing fractional doses of COVID-19 vaccines‘, CEPR Discussion Paper No. 16599. CEPR Press, Paris & London. https://cepr.org/publications/dp16599