Analysing data from controlled studies throughout the world, researchers discovered that people with hybrid immunity – from both full vaccination and prior infection – are the most protected against severe illness and reinfection. The study, published in The Lancet Infectious Diseases, will aid public policy-makers in planning the optimal timing of vaccinations.
Researchers from University of Calgary teamed up with World Health Organization (WHO) experts to answer the question of how well protected people are from combinations of vaccinations, boosters and prior infection.
“The results reinforce the global imperative for vaccination,” says 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.”
The global emergence and rapid spread of the Omicron variant required scientists and policy-makers 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, vaccination or hybrid immunity.
“Protection against hospitalisation and severe disease remained above 95 per cent 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 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 prior 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, 4268 articles were screened and 895 underwent full-text review – a difficult task before the assistance of experts in health informatics.
“This study demonstrates the power of machine translation. We were able to break through language barriers; most of the time, systematic reviews aren’t done in every language, they are limited to one or two,” says Dr Tyler Williamson “These former BHSc classmates, along with the large diverse team they brought together, have emerged as global leaders in SARS-CoV-2 research and delivered decision-grade evidence to the world.”
While the findings demonstrate that vaccination along with a prior infection carries the most protection, the scientists warn against intentional exposure to the virus.
“You should never try to get COVID,” says Bobrovitz. “The virus is unpredictable in how it will affect your system. For some, it can be fatal or send you to hospital. Even if you have a mild infection, you risk developing long COVID.”
The group says the next phase of this research would be to investigate how the bivalent vaccine performs against severe disease.
Findings from the study complement data on the SeroTracker dashboard which monitors studies and news reports to track seroprevalence data – the percentage of people in a population who have antibodies against the novel coronavirus. The website aggregates serology data from studies and news reports in different populations, and built-in filters allow users to compare seroprevalence levels between countries, occupations, and demographic groups.
Source: University of Calgary
