Over the last few months, a constant drum of headlines has highlighted the astonishing reality of the Covid-19 vaccines, especially mRNA vaccines manufactured by Pfizer-BioNTech and Moderna. The vaccines, study after study have shown, are more than 90 percent effective in preventing the worst outcomes, including hospitalization and death.
But next to this good news, there have been rare reports of severe Covid in people who had been fully vaccinated.
On June 3, for example, Napa County announced that a fully vaccinated woman who was more than a month past her second Moderna shot had died after being hospitalized with Covid. The woman, who was over 65 and had underlying medical conditions, had tested positive for the Alpha variant, which was first identified in the UK.
“I am very sorry that she had a sufficiently serious illness that it actually led to her death,” said Dr. William Schaffner, medical director of the National Foundation for Infectious Diseases and a vaccine expert at Vanderbilt University. But, he noted, “we expected to get an occasional breakthrough infection.”
Such cases should not deter people from being vaccinated, researchers said. “There is not a vaccine in history that has ever been 100 percent effective,” said Dr. Paul Offit, director of the Vaccine Education Center at the Children’s Hospital in Philadelphia. “This is your best chance to avoid serious, critical illness. But as is the case with everything in medicine, it is not perfect. ”
Severe Covid is rare in people who have been fully vaccinated. In a paper published last month, the Centers for Disease Control and Prevention said it had received reports of 10,262 breakthrough infections by April 30. It is only a small fraction of the 101 million Americans who had been vaccinated before that date, although the agency noted that it probably represented “a significant undercount” of breakthrough infections.
Of these breakthrough cases, 10 percent of patients were hospitalized, and 2 percent died – and in some of these cases, patients were hospitalized or died of something unrelated to Covid-19. The median age of those who died was 82.
Older adults at greater risk for Covid complications may also be more likely to develop pioneering infections because they are known to have a weaker immune response to vaccines. People who are immunocompromised or have other chronic health conditions may also be at increased risk.
Some of the variants – especially Beta, which was first identified in South Africa – may be more likely to evade the protection afforded by vaccines. But Beta is not currently common in the United States, Dr. Schaffner.
The alpha variant that infected the Napa County woman is highly contagious, but vaccines provide good protection against it – as well as against the original virus strain.
“Vaccines provide extraordinary protection against death and disease against the virus, and all residents should continue to be vaccinated to protect themselves and others,” said Dr. Karen Relucio, Napa County’s public health officer, in a statement.
Breakthrough infections are likely to decrease as more people are vaccinated and the transmission rate in the community decreases. “The virus will find fewer and fewer people to infect – it will be harder for the virus to work its way through the population,” said Dr. Schaffner. “These are good vaccines. In order for the vaccines to work optimally – on an individual and societal basis – as many people as possible must be vaccinated. ”