Hybrid immunity proves best defense against COVID-19 infection

Jan. 23, 2023

Results from global data show vaccination and a prior COVID-19 infection offer the best defense against severe illness and reinfection.

A University of Calgary research group joined forces with members of the World Health Organization (WHO) to tackle a global health question: What is the best protection against COVID-19? 

Analyzing data from controlled studies throughout the world, researchers discovered people with hybrid immunity are the most protected against severe illness and reinfection. Hybrid immunity occurs when someone has had at least the full series of vaccines, and has also had a prior infection, in any order. The study, published in The Lancet Infectious Diseases, helps public policymakers understand the optimal timing of vaccinations. 

“The results reinforce the global imperative for vaccination,” said Dr. Niklas Bobrovitz, first author on the study. “A common question throughout the pandemic was whether previously infected people should also get vaccinated. Our results clearly indicate the need for vaccination, even among people that have had COVID-19.” 

The global emergence and rapid spread of the Omicron variant of concern required scientists and policymakers to reassess population protection against Omicron infection and severe disease. In the study, investigators were able to look at immune protection against Omicron after a prior SARS-CoV-2 infection (the virus that causes COVID-19), vaccination or hybrid immunity. 

“Protection against hospitalization and severe disease remained above 95 percent for 12 months for individuals with hybrid immunity,” says Dr. Lorenzo Subissi, PhD, a technical officer with WHO and senior author on the study. “We know more variants are going to emerge. The study shows, to reduce infection waves, vaccinations could be timed for rollout just prior to the expected periods of higher infection spread, such as the winter season.” 

The systematic review and meta-analysis found that protection against Omicron infection declines substantially by 12 months, regardless of an infection, vaccinations or both, which means vaccination is the best way to periodically boost protection, and to keep down levels of infection in the population. In total, 4,268 articles were screened, and 895 underwent full-text review. 

The group says the next phase of this research would be to investigate how the bivalent vaccine performs against severe disease. 

University of Calgary release