Date/Time
Date(s) - 11/04/2024
11:30 am - 12:20 pm

Date/Time:  April 11, 2024 (11:30AM – 12:20PM)

Location:  HH 312

Speaker: Nir Gavish (Technion – Israel Institute of Technology)

Title: Epidemiology at Elevated Reproduction Numbers

Abstract:  During the COVID-19 pandemic, the emergence of the Omicron variant created an unprecedented scenario of an epidemic driven by a highly transmissible variant. Our data-driven research during that time showed that a variant with a basic reproduction number as high as 10 can defy conventional theory in certain circumstances.  Motivated by this experience, I will present two works focusing on the epidemic theory of highly transmissible variants:

1) Optimizing vaccine allocation is crucial for effective vaccination campaigns against epidemics. Contrary to intuition and classic vaccination theory, we show that for leaky vaccines and high basic reproduction numbers, the optimal allocation strategy for minimizing infections prioritizes those least likely to be infected. These findings have important implications for managing vaccination campaigns against highly transmissible infections. 

2) The competitive exclusion principle in epidemiology implies that when competing strains of a pathogen provide complete protection for each other, the strain with the largest reproduction number outcompetes the other strains and drives them to extinction. Various trade-off mechanisms facilitate the coexistence of competing strains in epidemic systems, particularly when their respective basic reproduction numbers are close so that the competition between the strains is weak. One may expect that a substantial competitive advantage of one of the strains will eventually outbalance mechanisms that facilitate coexistence, aligning with the principles of competitive exclusion. Yet, the literature lacks a rigorous validation of this statement. In this work, we challenge the validity of the exclusion principle at an ultimate limit in which one strain has a vast competitive advantage over the other strains.  Our results show that the competitive exclusion principle does not, unconditionally, hold beyond the established case of complete immunity.

 Joint work with Guy Katriel.