People with hybrid immunity are the most protected against severe illness and reinfection, a new study has found. Results from global data show vaccination and a prior Covid-19 infection offer the best defence against severe illness and reinfection, according to a University of Calgary research group.
Hybrid immunity occurs when someone has had at least the full series of vaccines and has a prior infection, in any order. The study published in The Lancet Infectious Diseases will help public policy makers understand the optimal timing of vaccinations.
"The results reinforce the global imperative for vaccination. 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 who have had Covid-19," said Dr Niklas Bobrovitz, first author on the study.
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 per cent for 12 months for individuals with hybrid immunity," said Dr Lorenzo Subissi, WHO-Scientist and senior author on the study.
The systematic review and meta-analysis find that protection against Omicron infection declines substantially by 12 months, regardless of whether you've had an infection, vaccinations, or both.
It means that vaccination is the best way to periodically boost your protection and to keep down levels of infection in the population. 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-19," said 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 a long Covid."