A huge number of people will need to receive a vaccine in order to stop the
A huge number of people will need to receive a vaccine in order to stop the
Afuture without the persistent threat of the coronavirus depends on a vaccine. Developing one is absolutely necessary “to return to a semblance of previous normality,” wrote Francis Collins and Anthony Fauci of the U.S. National Institutes of Health in the journal Science on May 11.
With more than 100 vaccines in development and a handful of them already being tested in human volunteers, public health officials are cautiously optimistic that one could be available as early as next year. Biotech company Moderna announced last week that its experimental Covid-19 vaccine produced an immune response in healthy participants in an early stage trial, but it still has a lot to prove.
The success of a vaccine hinges not only on its ability to protect against Covid-19 infection but also on how it’s rolled out to the public. Operation Warp Speed, the ambitious plan to rapidly develop a vaccine unveiled by the Trump administration on May 15, could play a crucial role in curbing the coronavirus pandemic in the United States. It aims to produce hundreds of millions of doses for Americans by January 2021, but it doesn’t detail a plan for getting them to citizens.
A huge number of people will need to receive a vaccine in order to stop the spread of the coronavirus and establish herd immunity — the point at which most of the population is protected against an infectious disease. To achieve herd immunity against Covid-19, experts estimate that around 70% or more of the population may need to be immune. And, since no vaccine is 100% effective, the more people who are vaccinated, the better. Getting a vaccine to all the people who need one will take a massive effort, both in the United States and around the world. There has never been a global immunization campaign on the scale that will be needed to distribute a Covid-19 vaccine.
If and when a vaccine does become available, there likely won’t be enough doses to give to everyone at once. That means governments will need to prioritize who gets it first.
“What it’s probably going to look like is a phased-in approach, with vaccines being rolled out to different target populations at a time,” says Maria Elena Bottazzi, associate dean of the National School of Tropical Medicine at Baylor College of Medicine and co-director of Texas Children’s Hospital Center for Vaccine Development.
Health care workers are an obvious first priority, since doctors, nurses, paramedics, nursing home workers, and other frontline responders are at high risk of contracting Covid-19 from infected patients. Moderna said in March that its vaccine could be available to health care workers as soon as this fall. But that’s assuming a lot goes right. Though Moderna’s vaccine is one of the most advanced coronavirus vaccines in development, there’s no proof yet that it can protect people against infection if they’re exposed to SARS-CoV-2, the virus that causes Covid-19.
Determining who should be in line to get a vaccine after health care workers will be a fraught decision. Adults 65 years and older are among the most vulnerable to severe illness and death from Covid-19, so it would make sense to protect them against infection. Prioritizing them could help prevent hospitalizations, freeing up hospitals that have been overwhelmed with sick Covid-19 patients. But some experts have raised concerns that a vaccine might not work as well in older people because the aging body tends to be less responsive to vaccination.
“Older adults generally don’t mount the level of immune response that you might hope for,” says Lois Privor-Dumm, director of policy, advocacy, and communication at the International Vaccine Access Center at the Johns Hopkins Bloomberg School of Public Health.
She says making sure older adults get vaccinated is more difficult than it is for children. In the United States, childhood immunization rates are more than 90% for most vaccines. That’s largely because infants get regular doctor visits before they turn two and because states have vaccination requirements for daycares and schools. Older adults might not be aware that they should get vaccinated for certain infections like flu, pneumonia, and shingles.
While vaccine programs have focused on children, Covid-19 is unlike many infectious diseases in that it doesn’t seem to cause serious symptoms in most children who get it. However, infected children can still pass the virus to others who may be at higher risk. Whether children should get a coronavirus vaccine before some adults will need to be debated.
Getting a vaccine to a large number of people could depend on what form it comes in and how many doses will be needed to provide an optimal immune response. A vaccine that requires two or more doses could complicate a rollout. Research on some multidose vaccines, like the human papillomavirus vaccine, shows that many don’t always get the necessary doses.
A potential complication of a vaccine rollout is that injectable vaccines need to be given by health care professionals. This means the number of people who could administer a vaccine is limited, which could slow its distribution.
Privor-Dumm says vaccine developers should be thinking about other formulations, like oral vaccines or skin patches, that could be more easily delivered, especially to children. Oral vaccines, which are given by squeezing drops into a child’s mouth, have been used for decades to prevent infections like polio, rotavirus, cholera, and typhoid. Skin patches are being investigated for a Covid-19 vaccine, but their effectiveness still needs to be proven. If they work, they could be delivered through the mail and applied like a Band-Aid.
The cost of a vaccine is another consideration. Vaccines are generally covered by health insurance without a co-pay. But many low-wage workers who are at higher risk of contracting the virus, like those who work in grocery stores, meatpacking plants, and warehouses, may not have insurance.
Government officials will need to figure out where people will get vaccinated. Requiring people to go to their regular health care provider could overwhelm doctor’s offices, and some workers may not be able to take time off to get a vaccine. Vaccinating people at workplaces, schools, or community centers could ensure that more people get vaccinated. Drive-through locations, like those that have opened for coronavirus testing across the United States, could also be used, but other options will be needed to accommodate people who don’t have access to a car.
“One of my concerns is that the people that need to get the vaccine most may not be able to access it,” Privor-Dumm says. “We need to make it convenient for people in places of risk to get a vaccine.”
Hannah Kettler, director of vaccine financing and partnerships at PATH, a Seattle-based nonprofit global health organization, says it’s worth considering that a vaccine will need to be distributed as social distancing policies are still ongoing, or perhaps revived, in some areas. That raises the question of how to logistically get a vaccine to people who are spread out and staying at home. Vaccination campaigns involve immunizing large numbers of people at a time. Even in a future where social distancing policies are relaxed, some still may not feel safe venturing out of their homes to go to a crowded place.
Even if a vaccine is highly effective, it’s unlikely that Covid-19 will disappear completely.
It will also be challenging to deliver vaccines to countries with weak health care systems, remote populations, and war zones. Many vaccines rely on a “cold chain,” a system of storing and transporting vaccines at certain temperatures in order for them to remain effective.
Issues of delivery aside, rolling out a coronavirus vaccine will require a “massive scale of manufacturing capacity” in order to produce enough doses, Kettler says. “There will need to be a combination of expanding on existing manufacturing capacity and also investing in new manufacturing capacity.”
Drug companies are pledging to deliver. The U.S. government has inked a $1.2 billion deal with AstraZeneca to secure at least 300 million vaccine doses. The British drugmaker has licensed an experimental vaccine from the University of Oxford. And Johnson & Johnson says it aims to produce 1 billion vaccine doses next year.
But it will take more than that to meet worldwide demand. “The ability to manufacture hundreds of millions to billions of doses of vaccine requires the vaccine-manufacturing capacity of the entire world,” wrote Collins, Fauci, and their co-authors Lawrence Corey and John Mascola in the May 15 Science article.
And manufacturing delays are almost certain, though some vaccines are easier to manufacture than others. Genetic vaccines, like the one Moderna, BioNTech, Inovio Pharmaceuticals, and others are developing, could in theory be manufactured more quickly than traditional vaccines. The main components of genetic vaccines — synthetic DNA or RNA — are cheap and easy to produce in the lab. Moderna was able to manufacture and ship doses of its RNA-based vaccine to the NIH for human testing in a matter of weeks. But genetic vaccines are not yet proven to work in people, and so far none have ever been licensed for sale, so no one is producing them in large quantities yet.
Bottazzi says we shouldn’t be too optimistic about vaccines that rely on new technologies because they’ve never been scaled up before. Her institution, Baylor College of Medicine, has partnered with PATH to develop a so-called subunit vaccine. The approach uses small fragments from a pathogen, as opposed to a weakened or killed version of the whole thing, to stimulate the immune system. Many licensed vaccines — like those for hepatitis B, HPV, and whooping cough — are made using this method. Bottazzi says a vaccine based on this type of existing technology could be scaled up faster because “many manufacturers already have all the capabilities, infrastructure, and expertise” to do it.
But established methods of making vaccines have their pitfalls, too. More than 80% of flu vaccines in the United States are made using a 70-year-old process that involves growing the influenza virus in chicken eggs. This method is time-consuming, taking months to produce the volume of eggs needed to mass produce the flu vaccine.
Shortages of materials to make vaccines could hold up the process in the same way that shortages of nasal swabs and other test kit components contributed to testing delays. Kettler says there will need to be enough glass vials to transport the vaccine, as well as syringes to administer it. Having multiple vaccines that come in different forms would be ideal, but only if they are all safe and effective.
If the botched rollout of diagnostic testing in the United States is any indication, getting a vaccine to a massive number of people will be complicated. Beyond logistical challenges, some people might be hesitant to get a vaccine because of misinformation and disinformation, which is already being propagated by a small but vocal minority. If and when a vaccine becomes available, Privor-Dumm says education and careful messaging will be needed to help people understand its benefits.
Even if a vaccine is highly effective, it’s unlikely that Covid-19 will disappear completely. Smallpox was declared eradicated in 1980 only after a decades-long vaccination campaign. Polio has yet to be fully eradicated around the world, despite a vaccine being available since the 1950s. A future without the coronavirus could be a long way off, but a vaccine that reaches the majority of people could hopefully vanquish the threat from our daily lives.