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A new CDC study provides another kind of good news about vaccines: Americans have been incredibly diligent about getting their second injection of Covid-19.
This was a real concern about the Pfizer / BioNTech and Moderna vaccines, the first two vaccines approved for emergency use in the United States, both of which have a two-dose schedule. As I wrote in December, the research literature on other multidose vaccines was troubling. About half of the patients never received their second or third dose.
An injection of these two-dose Covid-19 vaccines provides some level of protection, but in order to maximize an individual’s immunity and eliminate almost any risk of disease, the second injection is necessary. The less robust the immunity, the longer the Covid-19 could persist. This is why the CDC’s findings are so encouraging.
Nearly 9 in 10 Americans, 88%, who were eligible to receive a second dose of Pfizer / BioNTech or Moderna vaccines had received their second injection by mid-February. Almost all did so within the recommended time frame (17 to 25 days for Pfizer; 24 to 32 days for Moderna).
Another 8.6 percent of people who had their first stroke had not yet had their second but were still within the cleared range. Only 3.4 percent of people who received their first dose missed the window for their second injection.
The promising results come with a few caveats. First, many people who were vaccinated in the first wave were vaccinated at a workplace or at home if they live in a nursing home. This may have increased the two-dose schedule adherence.
“As priority groups get larger, adherence to the recommended dosage range may decrease,” warned the study authors.
People who must go out of their way to get vaccinated in a clinic or their doctor may not be as diligent as nurses or residents of retirement homes. Adherence to the multidose HPV vaccine, targeted at adolescents and young adults, is catastrophic.
Providers and public health workers administering vaccines have strategies to encourage people to take their second injection. Many schedule a second date when people get their first dose. Philip Huang, director of the Dallas County Texas Department of Health, told me in December that his agency would have access to a public database with every person who received a vaccine – and what vaccine they received – and that this information could be used to text patients reminding them to receive their follow-up dose.
But more targeted interventions might be warranted. The CDC study notes that American Indians and Alaskan Natives were slightly less likely than other demographic groups to get their second injection. Information about the race and ethnicity of people who receive a vaccine is not always reported either, so there may be other inequalities that the study was unable to detect.
Johnson & Johnson’s single dose vaccine is also now given more often. One of its main selling points is that there is no need to worry about a second dose (although the company has started testing second doses, especially with newer variants that continue to become dominant).
But aside from the asterisks, that’s still very good news. Ateev Mehrota of Harvard Medical School previously told me that the logistical challenges in ensuring patients receive a second dose are “enormous”.
At least so far America has risen to the task.
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