You're going to need more than one coronavirus shot. One vaccine dose likely won't be enough - experts
- A growing body of research shows that coronavirus antibodies may last just months.
- It's possible to get other coronaviruses more than once.
- This has implications for a Covid-19 vaccine. According to experts, it's likely people will need to be regularly revaccinated.
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We're all holding our breath for a coronavirus vaccine - for the day everyone can line up, get a shot, and then finally return to life as normal.
But there are many problems with that vision, a primary one being: We're all going to need more than one shot.
Research is coalescing around the idea that coronavirus antibodies dissipate after a period of weeks or months. Although our immune systems have more than just that one line of defence, those findings suggest that our immunity to the virus - whether generated in response to an infection or as the result of a vaccine - might be similarly transient.
Because the efficacy of a vaccine hinges on its ability to prompt the body to generate antibodies that protect you from future infection, it's likely that people will need two doses of a coronavirus vaccine a few weeks apart for it to be effective.
Some experts suggest we then may need to get regularly revaccinated.
"If immunity does turn out to be fleeting," disease ecologist Marm Kilpatrick told Business Insider, "we'll need a plan of a vaccination plus a booster, or revaccination at periodic intervals."
Leading drugmakers are already planning on a 2-dose vaccine regimen
Countless vaccines, like the one that protects against measles, mumps, and rubella, require back-to-back doses.
Some companies leading the coronavirus vaccine race are giving trial participants two shots three weeks apart. Pfizer is one of those: Early data showed that a two-dose regimen boosted the immune system response, with Pfizer researchers observing the highest level of neutralising antibodies one week after the participants' second dose.
Moderna's clinical trial involves giving participants two shots four weeks apart; AstraZeneca's ongoing trial, meanwhile, is testing outcomes from both a single vaccine dose and two doses given one month apart.
"This is probably going to be a two-series vaccine, which is not the end of the world. But it certainly would be far more convenient for it to be a single dose," Christopher Gill, an infectious disease researcher, told WBUR.
But it could be challenging for healthcare systems around the world to ensure that people come back for that critical second dose.
For example, research shows that less than one-third of young women who choose to get the first shot of human papillomavirus vaccine (HPV) - which primarily targets viruses than cause cervical cancer - return for the remaining two doses to complete the series.
Plus, a double-dose vaccine also requires twice as many vials, syringes, clinic visits, and so on at a time when such resources are already limited.
Then we might need booster shots
After that initial vaccination, regardless of whether it's one or two doses, regular booster shots might be necessary, too.
Some viruses, like hepatitis A or measles, are a one-and-done deal: once you're infected (or inoculated), you're immune for life.
"For human coronaviruses, that's not the case," Florian Krammer, a vaccinologist at the Icahn School of Medicine at Mount Sinai, previously told Business Insider. "You can get repeatedly infected once your immunity goes down."
Scientists haven't been able to study the new coronavirus long enough to determine how long immunity lasts, and there's no clinical evidence yet that anyone has been reinfected. But people can get other human coronaviruses (those that cause common colds) time and again.
"After infection with coronaviruses, re-infection with the same virus - though usually mild and only happening in a fraction of people - is possible after a period of months or years," according to the Mayo Clinic.
But it's not a deal breaker if people become susceptible to reinfection sometime after the initial shot, Krammer said.
"This happens for a lot of vaccines," he said. "It's not a problem. You can get revaccinated."
That's what booster shots are for. Your tetanus shot, for example, requires a booster every decade. The question is whether follow-up coronavirus vaccine shots will be needed on a scale of months or years.
According to Walt Orenstein, a vaccinologist and the former director of the US National Immunization Program, experts won't know whether boosters will become part of the protocol until the vaccine gets rolled out.
"Once we start seeing vaccine failures increasing, then we can consider booster doses. But we don't know at this stage whether that will be necessary," he told Business Insider.
But if it turns out that people need to be revaccinated regularly, that decreases the likelihood that people will get the shots they need to stay protected.
"The more complicated the schedule, the more difficult it is to get people to come in," Oreinstein said.
State and local officials should start educating Americans now about the importance of getting their required vaccine doses, he added.
"Vaccines don't save lives, vaccinations save lives. Vaccine doses that stay in vials are 100% ineffective," he said.
Andy Dunn and Hilary Brueck contributed reporting to this story.
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