The new Covid-19 vaccines’ success hinges on getting people to come back for a second shot after the first dose. That’s been a challenge in the past, and scientists fear skipped inoculations will drag out the pandemic.
Historically, a significant portion of people fail to follow through on vaccine schedules that require multiple doses; sometimes fewer than half of participants returned for the second shot. The leading Covid-19 vaccine candidates from Pfizer and Moderna both require two shots. If enough people skip the second injection, that risks prolonging the pandemic.
Scientists aren’t sure how effective only one dose of either vaccine would be, said Matthew Laurens, a principal investigator for the phase 3 Moderna vaccine trial based out of the Center for Vaccine Development and Global Health at the University of Maryland School of Medicine.
“You absolutely need need both doses,” Laurens said. “This ensures you get the full protective effect of the vaccine while minimizing potential side effects.”
Learning from history, it will be vital that states—which will organize most of the vaccinations—make the process as simple as possible so most people return for the second jab, Laurens said.
Hoping History Repeats
The last time the U.S. vaccinated massive amounts of people in a short time frame was for polio. Part of that vaccine distribution campaign was “Sabin Sundays,” named after Albert Sabin who developed the oral polio vaccine. On three consecutive Sundays in 1960, millions of Americans across the country got vaccines in local schools or churches, according to the University of Cincinnati Magazine.
Perfect compliance is unrealistic, Scott Knoer, CEO of the American Pharmacists Association, said. “Every time you have to do multiple doses it’s a challenge,” he said. But good public outreach encourages more people to get their second shot.
Replicating that success means putting vaccination centers as close to the people who need them most as states can—particularly historically underserved populations where transportation can be an issue. Offering evening and weekend vaccinations is also important to protect those who lack the luxury of working from home during regular business hours.
If it isn’t convenient, people are much less likely to come back for the second shot, and that undercuts herd immunity, Laurens said.
Federal officials will also have to follow through on promises to keep the shot free. Covid-19 testing was also supposed to be covered at no cost, but people reported getting bills for tests anyway.
No Playing Armchair Scientist
A botched AstraZeneca’s Covid-19 vaccine trial had surprising results. Some volunteers got only half a dose of vaccine in their first round, followed by a second, full dose. That smaller dose regiment of one and a half doses appeared to be more effective than two full doses.
While those results aren’t final, AstraZeneca officials say it’s worth looking into the issue. Until then, people need to get the full dose of the Covid-19 vaccine. That means states and scientists will have to be diligent to combat misinformation that may lead to some skipping the second shot.
That includes clearly communicating what side effects to expect. If people aren’t told to expect soreness or fatigue, which are common after getting shots, they might think something went wrong when those side effects occur.
“That could easily go the wrong way on social media or on other platforms where not just immediate contacts are influenced,” Laurens said. “We’ve learned we have to get buy-in from families and other community groups to advocate for vaccines, and it has to be available at many different locations.”