Delta illustrates benefits, limits of vaccines
Vaccine mandates growing in Massachusetts
By 
THE WORRYING SPREAD of the Delta variant has vastly changed the landscape around COVID-19 vaccines, putting renewed attention on getting everyone vaccinated while at the same time illustrating the limits of vaccination.
In Massachusetts, where around 64 percent of the population is vaccinated, Gov. Charlie Baker has strongly resisted imposing vaccine mandates or creating a state-level vaccine passport.
Yet Baker announced last week that he will require all staff at nursing homes to get a COVID shot. Health care leaders are increasingly embracing the idea of vaccine mandates for hospital employees – and in some cases for other publicly-facing workers. The Boston Teachers Union came out in support of a vaccine mandate for staff, as did SEIU Local 509, which covers human service and higher education workers.
In the last couple of weeks, the attorney general, treasurer, and auditor have said they will require their employees to be vaccinated.
Proponents of vaccine mandates say vaccines are the most effective method of stopping the spread of COVID-19 and stopping people from getting seriously ill and dying. Businesses say requiring the vaccine is the best way to keep employees – and customers – safe.
Yet the Delta variant has also illustrated some of the limits of vaccines. While the current vaccines protect people well against serious illness and death, there are an increasing number of breakthrough cases, where vaccinated people are both getting sick and spreading COVID.
Initially, both clinical trials and real-world data showed that the Pfizer and Moderna vaccines were 94 percent effective against infection. The Johnson & Johnson shot was 66 percent effective against infection, though the numbers are not comparable.
However, with the Delta variant becoming the dominant strain, several studies suggested the Pfizer vaccine is around 88 percent effective against Delta. One study from Israel showed its effectiveness is 64 percent against symptomatic illness, though still 93 percent effective against hospitalization. Studies of Moderna similarly show that it is effective against Delta – but likely not as effective as against the initial virus. There is limited data on Johnson & Johnson.
A back-of-the envelope calculation using Massachusetts data highlights this. For the week ending August 7, the Department of Public Health reported 2,232 breakthrough cases among 4.3 million fully vaccinated individuals – a rate of 51.6 cases per 100,000 people. If the remaining 4,652 cases that week were among an unvaccinated population of around 2.7 million, the rate among unvaccinated people was 171.8 per 100,000. That means a person is more than three times more likely to get COVID if they are unvaccinated, making the vaccines around 70 percent effective at preventing COVID cases.
Vaccines do play a major role in preventing severe illness and death and, accordingly, in preventing the hospital system from becoming overwhelmed. The Massachusetts data for August 1-7 reported 299 new hospital admissions, 50 among the vaccinated – a rate of 1.15 per 100,000 for the vaccinated population compared to 9.19 per 100,000, or eight times higher, for the unvaccinated population – giving vaccines an 87 percent effectiveness rate in preventing hospitalization.
This data are imperfect, the math is approximate, and there are significant differences between the vaccinated and unvaccinated populations – most notably, their ages. Dr. Ashish Jah, dean of the school of public health at Brown University, tweeted Tuesday that the national data show that vaccines prevent 75 to 85 percent of symptomatic infections and 90 to 98 percent of hospitalizations and deaths.
Harvard public health professor Yonatan Grad argues that past pandemics “have led to massive changes in the way we live that we’ve come to accept as normal.” COVID may do the same.