The number of countries affected by the Zika virus keeps growing—with the CDC reporting about 60 countries and territories with active Zika transmission—and a vaccine still a couple years away in the best-case scenario.
Following our update on the state of vaccine development efforts yesterday, Global Health NOW asked Bruce Y. Lee, MD, an associate professor of International Health and operations research director of the International Vaccine Access Center at the Johns Hopkins Bloomberg School of Public Health about the technical and ethical complexities of creating and administering a Zika vaccine.
Is there a way to create a universal vaccine platform for emerging pathogens—a basic way to stimulate the immune system, with the ability to add on specific antigens for each virus in question instead of starting over with every new threat?
Regarding universal platforms, researchers have been trying to do that with the flu vaccine. To do it for all viruses would be very difficult. Viruses are very diverse and many can mutate rapidly and significantly. It would be difficult to find a single common conserved region of the viral protein that is present in different viruses and also can generate an adequate immune response in people.
Once a vaccine has been developed, who needs to be vaccinated and what roadblocks might crop up in the path to delivery?
That has not been determined yet, and depends heavily on the characteristics of the vaccine: e.g., duration of protection, efficacy, cost, and potential side effects. The first target population will be those at high risk for Zika infection and consequences. So this could be pregnant women or those looking to conceive who are living in regions where Zika is widespread. Now of course, if you are giving something to pregnant women or those looking to conceive, you have to be particularly careful that the vaccine has minimal risk. Many may be reluctant to receive a completely new vaccine that has been developed so rapidly. Also, how is the vaccine going to be distributed to everyone? This would be a large undertaking that vaccine supply chains may not be ready to handle. Many of the world’s vaccine supply chains can’t even handle the currently available vaccines and adding a new vaccine could further clog up systems, which could hurt the control and prevention of other diseases.
Who will determine who (and which countries) will be first in line for vaccination, once a vaccination is ready for distribution?
It will be a combination of vaccine manufacturers, country governments, international organizations such as UNICEF, the WHO, and Gavi, the scientific community providing guidance, and wealthy donor countries who provide funding support for vaccine purchasing and distribution. The initial target countries have yet to be clearly determined. Although one may expect countries with higher Zika risk and burden such as Brazil to be possibilities. Within countries, specific higher risk populations may be targeted. This includes people living in areas of higher Zika transmission and those of childbearing age. Also, often vaccine introduction first occurs in locations that have already held clinical trials for the vaccine because those locations are already more familiar with the vaccine (its administration and side effects) and may have the necessary acceptance and infrastructure to support new vaccine introduction.
Do you see specific lessons for future Zika vaccines in the breakdown of yellow fever vaccine dissemination? For example, if the vaccines were delivered to, say, Brazil or Puerto Rico or Haiti first, is the infrastructure strong enough to ensure smooth delivery?
That’s a big issue right now. We know that many countries have limitations in their supply chains and can’t even get routine vaccines out to everyone, let alone a new vaccine. So it’s not a trivial issue. The options are to introduce the Zika vaccine, when it’s available, through routine existing vaccine distribution chains or to hold supplemental immunization activities, which are additional efforts to get vaccines to people such as using a campaign. Campaigns involve recruiting and mobilizing many people and setting up temporary vaccine storage and distribution centers. If there’s a feeling that the existing supply chain can’t handle Zika vaccine distribution, a country may consider a supplemental activity, especially when it wants to get people vaccinated quickly during an epidemic. But in addition to requiring many people to help with vaccination, campaigns require planning, organizing, and additional communications efforts and creative ways to publicize the campaign to get as many people vaccinated as possible. Both using the routine supply chain and supplemental activities will require additional efforts and cost money, but supplemental activities such as campaigns are much more expensive. Many countries cannot afford new vaccine introduction and thus require outside funding. Governments may not even have the personnel, equipment, vehicles, or infrastructure to do any type of new vaccine introduction. Therefore, external donors and organizations have to assist, such as wealthy countries either directly or through an organization such as Gavi. So who will pay for introducing the Zika vaccine is another big open question, especially when you are dealing with countries that are financially strapped right now, like Brazil.
Therefore, it is not enough to develop a new vaccine. While a vaccine is being developed, at the same time you have to plan how to distribute that vaccine. For one thing, it’s not as if other diseases go away when you have an outbreak. For example, focusing on Ebola during the outbreaks in West Africa may have resulted in measles outbreaks during the same time period. Our Highly Extensible Resource for Modeling Event-Driven Supply Chains (HERMES) logistics team, which draws on the expertise of the Johns Hopkins Bloomberg School of Public Health and Pittsburgh Supercomputing Center (PSC), has been trying to emphasize the importance of logistics planning whenever a new vaccine introduction is possible—using analytics such as computational modeling to help planning. A few years ago, Gavi, UNICEF, the WHO, and the Bill and Melinda Gates Foundation formed a hub to address various vaccine supply chain issues such as how countries can handle new vaccine introductions.
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