So-called “hybrid immunity” – from vaccination and infection – offers better protection against severe illness and hospitalization from COVID than immunity from infection alone, according to a new study published in Lancet.
The study provides recommendations to public health officials and policymakers about priorities when conducting vaccination campaigns, and about the potential frequency of booster shots moving forward.
The World Health Organization, which cooperated in the study, said on Wednesday that it “demonstrates the advantages of vaccination even when people have already contracted COVID-19.”
Those who developed hybrid immunity had a 95% lower chance of getting sick with COVID or needing hospitalization a year later, according to the study, which reviewed data from 26 other studies. Those who were previously infected but not vaccinated experienced reduced protection. The risk was only 75% lower, the researchers found.
Those who had hybrid immunity after the first two COVID shots were almost 42% less likely to be re-infected with COVID one year, and almost 47% less likely six months after the first booster vaccination. For those who have been infected but not vaccinated, protection is only 25% at 12 months.
Because those with hybrid immunity have the highest level of protection against COVID, in addition to the longest duration, they may wait six months after infection or vaccination to receive a booster dose, the authors said.
Governments could use the study’s findings to tailor vaccine recommendations to regions, the study suggests. If resources are scarce in an area commonly infected with COVID and there are competing health priorities, authorities may choose to focus on vaccinating high-risk individuals with only the two main vaccine series.
Since immunity against diseases and severe diseases is still strong throughout the year, mass vaccination campaigns can be carried out before the anticipated annual surge, such as in winter, the authors added.
However, he cautioned against creating nuanced vaccine guidance that is complex to understand and could reduce uptake.
Because Omicron is transmissible compared to previous variants of COVID, the rate of infection has increased and, thus, some measures of immunity, although decreasing, around the world, WHO said in a statement in June. In February 2021, shortly after the rise of Omicron, global public health organizations estimated that 16% of the world’s population had been infected. In October of the same year, that estimate rose to 67%.
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