Are enough people vaccinated to stop the spread of the virus?
The simple answer is no, experts say. In fact, the number of people who aren’t vaccinated opens the door for the virus to continue mutating, Gluckman said.
The only way to prevent the virus from mutating is to stop the virus from spreading. As long as the virus can multiply, it will make mutations, and some of those mutations can be problematic. If a virus mutates to the point that a vaccine becomes less effective or not effective, it’s back to square one, Gluckman said.
President Biden’s goal was to get 70% of the U.S. at least partially vaccinated by now. Some regions have reached that goal, while others have not.
Delaware reached Biden’s goal on Thursday, but vaccine statistics vary by area. For example, though parts of New Castle County have at least 60% partial vaccination, parts of Sussex County have fewer than 30% vaccination.
Philadelphia and Pennsylvania overall also have reached Biden’s goal. But as of June 25, counties like Bedford, Bradford, Clarion, and Clinton each had administered one dose to fewer than 50% of the population. In Fulton County, only 26% of people had at least one dose by June 25.
New Jersey overall also has reached Biden’s goal, but as of July 1, Cumberland County only had 46% of its population partially vaccinated.
Weiss said Biden’s goal has no scientific validity. He guesses that the number was influenced by projections early in the pandemic that 70% of people needed to be vaccinated to reach herd immunity.
The prediction, Weiss said, was based on what’s known as the basic reproduction number, or R0. That’s an epidemiologic metric used as an indication of the contagiousness or transmissibility of infectious agents. It’s measured by biological, sociobehavioral, and environmental factors.
The concept of herd immunity is that as more people have protective immunity, you will encounter fewer people who can be infected, so the infection doesn’t continue to spread as rapidly because it’s not finding susceptible hosts.
The problem, Weiss said, is that variants of the virus are quickly spreading.
“Though it’s the same overall virus, the nature of it has changed as these variants have had a chance to arise with the very, very rapid spread that we’ve seen around the world,” he said.
Another concern, Weiss said, is that people who are immunocompromised and people over the age of 80 might not be as protected by the vaccine to the same degree as other people.
“There’s already data showing that people who are over 80 really don’t in general get protective immunity after two doses. So they probably need a third dose,” he said. “And in addition, until they have that third dose, they should not assume they’re sufficiently protected, that they should keep up all the precautions we’ve been recommending for many months now in this pandemic.”
A person also needs the full two-dose regimen to be protected against variants. Therefore, Weiss argued, 70% partial vaccination is not something to be celebrated. The goal, he said, should be to get people fully vaccinated. Studies show that on average the second dose boosts antibodies about 15 times compared to the first dose.
Gluckman noted, however, that the current vaccines are effective.
“There’s been essentially no serious illnesses or deaths in anybody who has been vaccinated. They can catch one of these relatively resistant mutants, but the vaccine clearly helps them,” he said. “Now, that may not stay that way — as long as the virus is able to multiply, in the cohort of people that have not been vaccinated at all, the virus will continue to mutate. And there may be mutations for which the vaccines really don’t work. Now, they do.”
How do we end the pandemic?
Part of that has to do with preventing the virus from mutating, Gluckman said. The best way to do that is by vaccination.
Most RNA viruses don’t make perfect copies when they multiply. Instead, they make mutations. Many of these mutations do not benefit the virus, and the virus dies. But occasionally, a mutation can be beneficial for virus survival, either making it more contagious or more aggressive.
“You stop mutations by stopping the virus from multiplying, and today that really means vaccinating. I mean, you could shut down the world, but that’s a little impractical,” Gluckman said.
The fact that vaccination rates and COVID-19 case numbers vary from state to state, and that interstate travel is common, complicates the matter.
“Particularly when you’re getting a different message from one governor to the next,” Weiss said. “People sometimes believe what they want to believe. So if they hear someone say something that’s consistent with what they hope to believe, that’s what they do. And that really puts us back.”
“What we know with these types of viruses is it’s very hard to control them locally and they get out and spread. The best you can do is delay what happens in time. The vaccine, getting that out rapidly, really helps stop or suppress this virus from getting into communities. So we’re much better off than we had been,” he said.
“I am concerned that the general tone of conversation is that, ‘We’ve got this beat. You don’t have to worry. We can relax all of our precautions.’ And I don’t think that’s quite [where we are] right now,” Weiss added.
The Centers for Disease Control and Prevention recently concluded that the Delta strain is increasing, and that within the next few months it will likely be the dominant strain of the virus. Weiss said researchers need to continue studying variants, and examine people with mild infections or who are asymptomatic to better understand the dynamics of spread, and to what degree the current vaccines offer protection.