In light of new evidence that vaccinated people with breakthrough infections can carry as much coronavirus as unvaccinated people, the Centers for Disease Control and Prevention has urged people in high-transmission areas to wear masks in public indoor spaces regardless of their vaccination status.
Vaccines remain highly effective in preventing serious illness and death, but the highly contagious Delta variant and ongoing vaccine denial have led the United States in an unexpected direction. The reported cases are at their highest level in six months.
Still, most vaccinated individuals with breakthrough infections are likely to have mild symptoms, and any exposure to the virus is an opportunity for the immune system to strengthen its defenses against future variants.
Here’s what you should know about breakthrough infections and the Delta variant:
The vaccines were designed to prevent hospitalizations and death, largely due to damage to the lungs and other organs. The vaccines produce antibodies in the blood that prevent the coronavirus from taking root in these organs.
At the onset of infection, when people are most likely to be contagious, the Delta variant appears to replicate in amounts perhaps 1000 times that of people infected with other variants and defeat the immune defenses in the nose and throat .
Some experts believe that breakthrough infections are more likely after exposure to the Delta variant than after previous forms of the virus. Even as newer data become available, it is likely that most hospital admissions and deaths from Covid-19 will occur in unvaccinated people.
In some rare cases, breakthrough infections can lead to persistent symptoms. “Long Covid” is a poorly understood set of symptoms that can affect people for several months after an active infection has ended. A few small studies have looked at how common or how severe Covid can be after breakthrough infections. It’s likely rare, say some experts, because breakthrough infections are rare and of shorter duration.