With COVID-19 vaccines still in limited supply and case counts threatening to resurge, there is a debate over the benefits of giving more people their first shot and waiting a longer time to administer the second dose, or whether to stay the course and prioritize getting both doses of the Pfizer and Moderna vaccine into arms as quickly as possible.
Seattle-area health experts have differing views.
Virologist and vaccine scientist Dr. Larry Corey came out in favor of the two-shot strategy in a recent editorial on the Timmerman Report. Corey, the past president of the Fred Hutchinson Cancer Research Center, argued that giving a single dose risked creating an environment hospitable to new, more dangerous mutations of the COVID virus.
Corey writes: “…the virus, when it gets inside a host with only partial immunity, has a greater opportunity to linger inside the body and keep replicating until it develops certain evolutionary advantages….[It] makes sense to make the virus face off with our most formidable immune defenses. We force it to go up against people who have been fully immunized with the two-dose vaccine regimen.”
One Shot or Two? Read why virologist Larry Corey believes it's best to stick with the two-dose vaccine regimen. @fredhutch @uwmnewsroom https://t.co/1chueuG6JJ
— Luke Timmerman (@ldtimmerman) March 14, 2021
The question of whether to delay a second dose does not apply to the newly approved Johnson & Johnson vaccine, which does the job with one shot.
Lab experiments have shown that both the so-called United Kingdom variant and the South Africa variant of COVID require a more robust immune response to fight the virus. In Washington, 146 cases of the UK variant, or B.1.1.7, have been found, along with eight cases of the South Africa variant, B.1.351, and two cases of the Brazil variant, P.1.
Michele Roberts, acting assistant secretary for the Washington State Department of Health, on Thursday urged residents to get their booster for the two mRNA vaccines according to the original schedule. For Pfizer that’s three weeks after the first shot, or four weeks after the first shot of the Moderna vaccine. In Washington, nine out of 10 people are getting the second dose on schedule.
Earlier this month, Dr. Anthony Fauci, the top infectious-disease expert for the U.S., likewise defended the two-dose approach.
The case for a delayed second shot
Ruanne Barnabas, an epidemiologist with the University of Washington’s Department of Global Health, has a different take.
“Everyone should get one dose as quickly as possible and as we have enough supply. We can catch up with the second dose,” said Barnabas, who published an opinion piece earlier this year in the Annals of Internal Medicine.
Studies show that a single dose had more than 50% efficacy for both mRNA vaccines, and perhaps more, Barnabas said. And it’s unknown how strong of an immune response is needed to stop the infection. The quick schedule for the booster was driven in part by the urgent need to get a vaccine approved for use, the UW associate professor said, versus medical necessity. Other vaccines, while not based on mRNA technology, commonly have a six-month delay before a second booster shot.
Dr. Jeff Duchin, who leads Public Health – Seattle & King County, responded to a tweet regarding Corey’s editorial, offering “another perspective.” While Duchin didn’t explicitly take a side, he cited two studies examining the impacts of giving one dose and delaying the booster. One article suggested more lives could be saved by favoring the roll out of initial doses. The other reported that a partial vaccination using the Pfizer vaccine was 63% effective in preventing infections in a nursing home facility.
A separate study from Israel not referenced by Duchin found that the Pfizer vaccine reduced COVID infections by 85% some two weeks after administering the first shot.
The double dose of the mRNA vaccines are about 95% effective. The Johnson & Johnson vaccine is 66% protective against moderate to severe infections. Experts note that the earlier vaccines were tested during a time when the number of cases was lower and variants less prevalent, so the Johnson & Johnson vaccine might actually stack up more favorably to the Moderna and Pfizer vaccine than the data suggest.
To gain federal emergency approval for use, the COVID vaccines needed only to be 50% effective.
In contrast to the U.S., the United Kingdom has prioritized more widespread coverage through the delayed second-shot approach, and now more than half of the adult population has received at least one dose.
The average number of new cases in England is 8 per 100,000. By comparison, that rate is 9 per 100,000 in Washington state, according to the New York Times.
The call for a change to the U.S. approach includes Sen. Chris Van Hollen (D-Md.) and Sen. Martin Heinrich (D-N.M.). “Recently published real-world data suggests a single dose offers effective protection against severe illness, hospitalization and mortality,” the senators wrote in a letter to the Biden administration on March 1.
Here are some of the arguments for both sides, based on research and expert commentary:
Two shots: one shot, then a booster 3-to-4 weeks later
- This is the strategy backed by the most robust research for the Pfizer and Moderna vaccines.
- The two-dose regimen is a safer bet for preventing infections against variants, given the increased ability to some to defy vaccinations.
- There are concerns that if the second dose is delayed too long, people will lose their resistance to the virus, and/or a second dose won’t give the necessary boost, requiring a third dose.
- Millions of doses of vaccines are on the horizon, Fauci said, including the Johnson & Johnson vaccine.
- Changing the strategy for giving boosters threatens to erode confidence in the vaccines.
One shot, then a delay of the second of up to 12 weeks
- Research, while limited, shows a significant level of protection against COVID from a single dose of Pfizer and Moderna vaccines.
- Among healthy people, a single dose could reduce the spread of the disease, including variants.
- There is a push nationwide to get schools and businesses reopened, and essential workers are eager for protection. Barnabas argues that offering one dose to more people is a more equitable solution while the vaccine is limited.
- Despite promises of millions of vaccines, manufacturers have sometimes fallen short on their commitments.
Promise of more vaccine doses
In Washington state, 21% of people have received at least one dose, and 12% are fully vaccinated. More than 2.5 million doses have been administered in total, with about 44,000 injections daily.
At the same time, the decline in infections that followed the surge during the winter holidays has plateaued in many places. Experts worry about the risk of a fourth wave of illness. Washington’s restrictions on gatherings and business operations are loosening on Monday, and soon more kids are returning to in-person instruction.
Gov. Jay Inslee on Thursday announced that an additional 2 million people will be eligible to receive the vaccine by the end of the month. That includes people 60 and over; those with health conditions that put them at increased risk of COVID; pregnant women; people living in group settings such as prisons, homes for those with disabilities, those experiencing homelessness; and workers in restaurants, manufacturing, public transit, agriculture, construction and other settings. 
That will bring the total number of Washington residents eligible for the vaccine to 5 million. The state has approximately 6.2 million residents age 16 and older, and 1.4 million under 16. The Pfizer vaccine is approved for people 16 and older, while the Moderna and Johnson & Johnson vaccines are approved for people 18 and older. The vaccine makers are launching studies in tweens and teens 12 and older.
By May 1, all residents age 16 and older will be eligible to receive the vaccine, as proclaimed by President Biden earlier this month.
“Looking ahead, we’re hearing good news from the federal government about vaccine supply,” said the Department of Health’s Roberts.
This week, the state received its first shipment of the Johnson & Johnson vaccine, with 8,400 doses. Washington officials expect to receive a total of about 345,000 doses of the different vaccines each week through early April, which is still 110,000 short of what providers are asking for, Roberts said. In April, the allotment could go up to about 600,000 doses a week.
The infrastructure needed to deliver the shots is ramping up in Washington. The city of Seattle has Lumen Field — home to the Seattle Seahawks — ready to deliver up to 22,000 doses daily.
