A new CDC study offers a different kind of good news about vaccines: Americans have been incredibly diligent about getting their second Covid-19 vaccine.
This was a real concern in relation to the Pfizer / BioNTech and Moderna vaccines, the first two vaccines approved for emergency use in the United States, both with a two-dose schedule. As I wrote in December, the research literature on other multi-dose vaccines was worrying. Approximately half of the patients never received the second or third dose.
An injection of these two-dose Covid-19 vaccines provides some level of protection, but to maximize an individual’s immunity and almost eliminate the risk of any disease, a second injection is necessary. The less robust the immunity, the longer the Covid-19 can last. That is why the CDC’s findings are so encouraging.
Nearly 9 out of 10 Americans, 88 percent, who were eligible to receive a second dose of the Pfizer / BioNTech or Moderna vaccines, had received their second injection in mid-February. Almost all of them met the recommended deadline (17-25 days for Pfizer; 24-32 days for Moderna).
Another 8.6% of the people who hit the first attempt had not yet hit the second, but were still within the allowed range. Only 3.4% of people who took the first dose missed the second dose window.
The promising results come with some caveats. First, many of the people who were vaccinated during the first wave were vaccinated in a workplace or at home, if they lived in a nursing home. This may have increased adherence to the two-dose regimen.
“As the priority groups expand, adherence to the recommended dosage range may decrease,” warned the study’s authors.
People who need to work hard to get the vaccine at a clinic or their doctor may not be as diligent as nurses or nursing home residents. Adherence to the multi-dose HPV vaccine, aimed at adolescents and young adults, is terrible.
Providers and public health professionals who administer vaccines have strategies to encourage people to follow up for the second injection. Many are scheduling a second appointment when people receive their first dose. Philip Huang, director of the Dallas County Texas health department, told me in December that his agency would have access to a public database of each person who received a vaccine – and which vaccine they received – and that information could be used to send text messages to patients reminding them to take their follow-up dose.
But more targeted interventions can be justified. The CDC study notes that American Indians and Alaskan Natives were slightly less likely than other demographic groups to get their second chance. Information on race and ethnicity of people receiving the vaccine is not always reported, so there may be other inequities that the study was unable to detect.
The Johnson & Johnson single-dose vaccine is also being administered more frequently. One of its biggest selling points is that there is no need to worry about a second dose (although the company has started testing the second doses, especially with the new variants continuing to become dominant).
But aside from the asterisks, it’s still good news. Ateev Mehrota, from Harvard Medical School, told me earlier that the logistical challenges in ensuring that patients received a second dose were “huge”.
At least so far, America is up to the task.