Vaccine hesitancy could make it difficult to achieve herd immunity for COVID-19
Anthony S. Fauci, MD, told CNN last month that it is unlikely a COVID-19 vaccine with an efficacy of up to 75% that is taken by two-thirds of the population would be enough to create herd immunity against the novel coronavirus.
"The best we've ever done is measles, which is [97% to 98%] effective," Fauci, the director of the National Institute of Allergy and Infectious Diseases, told the network. "That would be wonderful if we get there. I don't think we will."
According to an ABC News/Ipsos poll, one-fourth of Americans said they would refuse a COVID-19 vaccine if one was available. In a CNN poll, even more respondents — one third — said they would not try to get a vaccine.
As case counts rise across the United States, the urgent need for a vaccine remains, but experts worry that vaccine hesitancy could make it more difficult to achieve herd immunity for COVID-19.
“We are in an era of anti-vaccine sentiment, and I think that there will be hesitancy by some to try a new vaccine,” Amesh A. Adalja, MD, senior scholar at Johns Hopkins Center for Health Security, told Healio. “It will be very important for public health authorities to communicate what is known about the vaccine and what its safety profile is.”
In general, with a virus as contagious as SARS-CoV-2, around 60% of the population would need to be immunized to reach the herd immunity threshold, Adalja said.
“That assumes a very homogenous population, and obviously there are people at different risks,” he said. “There is modeling that shows that maybe you can get away with a lower threshold if you are vaccinating high-impact individuals because they may be contributing more to spread than others.”
Adalja said physicians can reassure patients of the safety of any COVID-19 vaccine by discussing studies that led to its approval, talking about the vaccine’s side effects and in what populations they commonly occur, and explaining the vaccine’s benefits and overall risk for COVID-19 to the vaccine recipient. He said comparisons to noteworthy vaccination campaigns from the past — including for polio, smallpox and influenza — can be useful.
“I do think it is challenging to be able to make a vaccine to vaccinate the entire population,” Adalja said. “We have to ensure that manufacturing capacity is sufficient and that we have the ability to distribute the vaccine to health care providers. We also have to be prepared for any kind of hiccups that may occur during production scale up.”
- ABC News. Reopening the country seen as greater risk among most Americans: Poll. https://abcnews.go.com/Politics/reopening-country-greater-risk-americans-poll/story?id=70555060. Accessed July 1, 2020.
- CNN. Fauci says Covid-19 vaccine may not get US to herd immunity if too many people refuse to get it. https://www.cnn.com/2020/06/28/health/fauci-coronavirus-vaccine-contact-tracing-aspen/index.html. Accessed July 1, 2020.