Covid “breakthrough” cases explained

Most hospitalisations and deaths from coronavirus have occurred among unvaccinated individuals, yet there have also been so-called breakthrough infections of fully vaccinated people


Why breakthrough cases occur
No vaccine is 100 percent effective at preventing infection in all cases. As more people have become vaccinated against Covid-19, so number of breakthrough cases has increased

Natural virus evolution
SARS-CoV-2 continues to mutate into variants that are more infectious and more adept at evading immunity provided by vaccination or previous Covid-19 infection

Vaccine effectiveness
Research shows most vaccines
are working to dramatically decrease risk of hospitalisation and death, even against highly-transmissible Delta variant. For example, Pfizer vaccine is 96 percent effective against hospitalisation from Delta variant after two doses

Individual immune response
Chances of getting seriously ill after vaccination are higher for those people with health conditions that affect immune system. Even in those with good immunity, vaccine protection is likely to wane over time

Severity of illness 
Infections among vaccinated people tend to be mild, with fewer symptoms. Severe cases are extremely rare
As of July 12, out of 159 million fully vaccinated people, CDC* recorded 5,492 cases who were hospitalised or died from Covid-19 (equivalent to less than 1 in 29,000)

Share of cases aged 65 or over
75% 
19 percent of total cases died


*Centres for Disease Control and Prevention
  

Sources: Bloomberg, CDC, NPR 
Picture: Getty Images 
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