Via STAT, Dr. Seth Berkley of GAVI, writes: Learning from the yellow fever vaccination campaign. Excerpt:
To cope with this yellow fever emergency, the World Health Organization has taken the unusual step of recommending the use of fractional doses — each person will get one-fifth of the normal dose. Although this makes it possible for more people to get vaccinated, it also offers challenges such as finding enough smaller syringes and training health care workers in different methods of preparing and performing the injection.
This isn’t the first time that fractional dosing has been used. Much of the emergency smallpox vaccine stockpile in the United States is made up of fractional doses. With the rising risk of urban epidemics, and until emergency stockpiles reflect the size of that risk, fractional dosing may be the only way of ensuring that everyone is protected, not just those living in wealthy countries or countries with their own vaccine manufacturing facilities.
And yet there are still important unanswered questions about fractional dosing. In the case of yellow fever, we don’t know if fractional doses provide lifelong protection against the virus, as full doses do. Research suggests that fractional doses should provide protection for at least 12 months which, in the short term, may help prevent the spread of the yellow fever in Angola and the DRC and buy some time while vaccine stockpiles are replenished. The intensive vaccination campaign will provide crucial information on the duration of protection.
Yellow fever comes and goes in humans because the virus also lurks in monkey populations. New outbreaks tend to begin along the edge of natural forest habitats when unimmunized individuals come in contact with mosquitoes that have bitten infected monkeys. In such situations, rapid outbreak response campaigns can be conducted in affected communities that create a wall of immunity around those infected and bring the outbreak to a quick end.
But climate change is altering where and when disease-carrying vectors like Aedes aegypti live. Human settlements are encroaching on forested areas. Plus there’s a global trend towards urbanization, with more people living closer together.
The combination of these three changes creates a very real potential for larger outbreaks than we’ve ever seen before. That’s why it is so important to vaccinate everyone in Kinshasa and elsewhere in Angola and the DRC. Subscribe to The Readout: A guide to what's new in biotech