Evaluating COVID-19 Vaccine Efficacy Using Regression Discontinuity Design

Strategic Insights -

In an effort to contain the coronavirus disease 2019 (COVID-19) pandemic, the United Kingdom initiated its vaccination campaign on December 8, 2020. To date, more than 77% of the adult population in the U.K. have received at least one dose of the COVID-19 vaccine. A new study published on the preprint server medRxiv* estimates vaccine effectiveness against COVID-19 mortality in England using the regression discontinuity design (RDD) approach. This study evaluates the effectiveness of the COVID-19 vaccine in real-world settings, considering the impact of confounding factors and temporal changes.

Key Takeaways:

  • The study used a fuzzy RDD method to estimate the impact of vaccination on the risk of death due to COVID-19 in England, exploiting the discontinuity in vaccination rates generated by the U.K.'s age-based vaccination strategy.
  • Researchers found a reduction in mortality rates due to COVID-19 for people above the age of 80 years, indicating that the reduction was largely due to the availability of vaccines rather than residual confounding factors.
  • The RDD approach estimated vaccine effectiveness to be 70.5% for the vaccinated group who were of or above 80 years and seropositive, with a single dose of the COVID-19 vaccine providing a robust protective effect against COVID-19 mortality in the older age group.
  • The study estimated that approximately 93.9% of England's population in the age group of 7584 years had received the first dose of a COVID-19 vaccine.
  • The study's main strength is the use of the RDD method to estimate COVID-19 vaccine effectiveness, minimizing the risk of bias and considering confounding factors.
  • The study's limitation is that it has only estimated the effectiveness of the first dose of the COVID-19 vaccine and did not consider immune responses that may have occurred due to previous COVID-19 infection.

Statistics:

  • More than 77% of the adult population in the U.K. have received at least one dose of the COVID-19 vaccine.
  • The study estimated that approximately 93.9% of England's population in the age group of 7584 years had received the first dose of a COVID-19 vaccine.
  • Vaccine effectiveness was estimated to be 70.5% for the vaccinated group who were of or above 80 years and seropositive.
  • A single dose of the COVID-19 vaccine provided a robust protective effect against COVID-19 mortality in the older age group, with a reduction in mortality rates due to COVID-19.

Sources:

  • medRxiv*, preprint server
  • Medicines and Healthcare products Regulatory Agency (MHRA)
  • Pfizer-BioNTech (BNT162b2)
  • Moderna (mRNA-1273)
  • Oxford-AstraZeneca (ChAdOx1)
  • Legal Monitor Worldwide
  • SyndiGate Media Inc.