Millions of Americans are not getting their second dose of the coronavirus vaccine within the recommended time period for ensuring optimal protection from COVID-19, according to a CBS MoneyWatch review of the latest data from the U.S. Centers for Disease Control and Prevention.
As of Wednesday, just over 2.8 million Americans who had received their first shot — nearly 12% of those vaccinated — had not gotten their second dose within the 28-day interval prescribed for Moderna's vaccine, one of two approved for use in the U.S. The other vaccine, jointly produced by Pfizer and Germany's BioNTech, is supposed to be administered 21 days after getting a first dose.
The number of people who have yet to get their second vaccine dose is based on the latest public data from the CDC. Vaccine and health care experts who reviewed the figures for CBS MoneyWatch said it jibes with scattered reports of delays in people getting both shots within the suggested time frame.
"I am hearing anecdotally about people trying to schedule their second shots and having challenges doing so," said Bruce Y. Lee, who studies health management and public policy at the City University of New York. "It is challenging to do a vaccine rollout, even more so when it involves two shots. All of this should've been planned last year in advance of the rollout, and this is more evidence that it wasn't."
As of the end of January, 96% of Americans who had gotten their first vaccine shot had received their second within four days of the properly prescribed interval, according to earlier CDC data obtained by CBS News. But the agency has not released an update on how the country is doing in administering both shots within the recommended period.
In the meantime, the share of people getting their second dose on time has been shrinking — and the gap, which topped 1 million only a week ago, has been growing rapidly, to 2,826,134 people as of February 24.
A spokeswoman for the CDC said that a portion of the recent slowdown, in getting both first doses and second doses administered, has been due to the weather. She said the CDC is planning to release new information on second dose completion rates soon.
Hospital administrators and state health officials who spoke with CBS MoneyWatch attributed the delays in people getting their second shot to a shortage of vaccine doses as well as to scheduling and shipping snafus.
Seemingly less of a concern, according to health professionals, is Americans simply choosing to skip their second shots, an issue that experts had warned could undermine the vaccine rollout.
Dr. David Basel, head of vaccinations for Avera Medical in Sioux Falls, South Dakota, one of the biggest health care networks in the state, said no-shows for the second shot accounted for less than 1% of all vaccinations there. The biggest reason people don't show up between shots is an illness in the interim, he added: "We are vaccinating the elderly and most at-risk populations first. People get sick, and it's often not with COVID."
A lack of vaccine to supply the second doses seems to be a key issue for hospital systems. Jessica Daley, a pharmacist and vice president with Premier, which purchases medical supplies for thousands of hospitals in the U.S., said many hospitals were instructed to use every dose they had for first shots and that more supplies would be coming. Recently, however, they have seen their shipments drop. In the past few weeks, a number of states have shifted more vaccines to pharmacy chains or mass vaccination locations and away from hospitals.
"We did a spot survey, and the No. 1 concern from hospitals is actually getting the vaccine," Daley said. "I have heard of hospitals not getting those second doses."
More encouragingly, some health experts think that delays in second doses of vaccine does not doom the U.S. vaccination effort. Earlier this month, the CDC released new guidance that second shots could be administered as late as 42 days after the first dose, although the agency reiterated that a second jab within 21 or 28 days was optimal.
Recent early studies also suggest that a single shot still provides significant protection against spreading the coronavirus, though not as much as two shots do.
"In the grand scheme of things, when you look at the other problems we are having, this is a minor issue," said Will Humble, a former top public health official in Arizona.
Humble also said ensuring that more people get a first dose, rather than completing second doses, would make the vaccine rollout more equitable for minority communities and still likely lower infection rates overall.
"We have boxed ourselves into a less efficacious way of saving lives because of the way the trials were formulated," he said of the initial emphasis on administering two doses.
Still, most health experts advise that individuals try to adhere to the recommended intervals for getting two vaccine shots. Tinglong Dai, a professor of health management at Johns Hopkins Carey Business School, said vaccine supplies are not increasing as fast as needed to continue the current pace of vaccinations. States will need to hold back more doses to ensure they have enough to deliver a second dose within the appropriate time frame, he added.
Earlier this week, Dai released a study with two co-authors from Oxford University and the University of California at Berkeley that found that releasing more second doses to increase the number of people who get at least one shot does not lower coronavirus infection rates. The paper did find that lengthening the time between doses does still slow the rate of infection, but will ultimately lead to more cases as the pandemic drags on.
"I do think distribution is going to get better," Dai said. "But unless the supply of vaccine increases exponentially, we are going to have a growing backlog [of people waiting for that second shot]."