The Centers for Disease Control and Prevention (CDC) has released good news/bad news data on the proportion of Americans who are following through with a second COVID-19 vaccine dose, according to the New York Times. The report is not available online at time of writing, but if the reports are correct the rate of second doses is actually impressively high by comparison with past campaigns, but the downward trend in second doses puts the goal of herd immunity in danger.
In March, the CDC reported that an encouragingly low 3.4 percent of early recipients of the Moderna or Pfizer vaccine had missed their second dose. Multiple outlets claim updated figures up to April 9 show that has risen to 8 percent among those whose first round was in late January or February. Although the roughly 92 percent completion rate compares well with many previous public health campaigns (for example, Hepatitis A and B completion rates in 2018 were 30-40 percent), the presence of 5 million people with only partial immunity could be a problem, particularly if they think they have all the protection they need.
Anti-vaxXers are spinning the news as a sign people are changing their minds about vaccination after their first dose. However, there is little evidence many people are deliberately refusing to get the second shot.
Instead, there appear to be many reasons why people are missing a second vaccine, making it unlikely any single approach will fix the problem. The New York Times reports a mixture of scheduling problems, temporary shortages of vaccines, and people with too many other things to do as their life starts to return to normal. Complacency is likely also an issue, which could become worse where new infection rates are falling.
A consequence of the multiple vaccines currently available is that some people whose first shot was of one variety of vaccine sometimes get offered a different one for their booster. Some experts think mixing and matching may not be a problem, particularly between the two mRNA vaccines, but as the idea is sufficiently untested most are wary.
There could be an even larger problem in places, particularly the UK, that deliberately vaccinated as many people as possible once before making the second round widely available. The approach has both advantages and risks, with one of the latter being that people are more likely to forget to return once a longer period has passed.
A single dose of all the authorized vaccines provides some protection against catching COVID-19, so it is definitely better for people to get one dose than none. Moreover, even getting both shots is no perfect guarantee. Nevertheless, with varying estimates of the protection offered by a single dose, stopping community spread will require most people to get both rounds. According to the CDC, currently, 141 million people in the US have had their first dose, and 95 million have had both.
It's important to note IFLScience hasn't been able to verify the CDC data seen by the New York Times, as it does not appear to be available to the public. However, despite the focus appearing to be on the drop in people getting their second dose, if the reported 92 percent that have is verified, this is a highly successful vaccine campaign.
Any vaccine that requires two doses will have a problem with some people failing to get their booster shot. So far COVID-19 vaccinations have a better completion rate than the Shingrix vaccine against shingles, where just 70 percent of American recipients get their second dose within the recommended six months, and 80 percent within the year.
Meanwhile, the CDC also noted the pandemic has caused many children to fall behind in routine vaccinations for other conditions. They're hoping Infant Immunization Week (April 24-May 1) will encourage many parents to catch up.
[H/T: The New York Times]