The reports of fully vaccinated people testing positive for coronavirus disease (Covid-19) has caused concern for the authorities around the world who were depending on vaccination to contain the virus surge. While the ‘breakthrough’ Covid-19 cases raise questions about the efficacy of vaccines, especially against the highly contagious Delta variant, health experts have said that they are not a cause for alarm.
What are breakthrough cases?
When a fully vaccinated individual gets infected with coronavirus, it is termed a breakthrough case. UK health secretary Sajid Javid, some White House staffers, and athletes taking part in the Tokyo Olympics testing for Covid-19 are examples of breakthrough cases.
Covid-19 vaccines generate neutralizing antibodies that work with the rest of the immune system to destroy the pathogen whenever the body is exposed to the virus. Recent studies have suggested that Pfizer-BioNTech, Moderna and AstraZeneca vaccines have been highly effective against Sars-Cov-2.
However, the same vaccines have shown reduced efficacy against the Delta variant which has been identified in at least 124 countries and is rapidly becoming the dominant variant across the world. But it is still good at protecting people from severe illness – a strong reason to get vaccinated.
Why do breakthrough cases occur?
Dr William Moss, a vaccine expert at the Johns Hopkins Bloomberg School of Public Health, said it’s difficult to determine the reason behind a particular breakthrough case but viral load could be a factor in such infections. Moss said that underlying health conditions or medications taken by them could make their immune system less responsive to the vaccines. He added that most people with breakthrough infections experience mild illness.
The US Centers for Disease Control and Prevention (CDC) has said that vaccine breakthrough cases are expected since no vaccines are 100% effective. It also noted that a small percentage of fully vaccinated people will get sick, hospitalised and even die from Covid-19. While the current data, as per the CDC, suggest that Pfizer and Moderna vaccines offer protection against most variants, however, they will cause some vaccine breakthrough cases.
(With AP inputs)