New Year’s Day may usher in a new decade, but our crystal ball suggests some old problems will remain key global health issues in 2020.
We’re sticking out our neck a bit and leaving the long-long-long-running Ebola outbreak in the Democratic Republic of the Congo off our list of top public health stories to watch in the coming year. Call us crazy optimists — no one ever has before! — but we’re hopeful that despite recent violence in the outbreak zone, the downward trend that has accelerated in recent months means this nightmare epidemic will finally end sometime in early-ish 2020. Warning: The final few miles of the road will likely be bumpy.
So Ebola aside, what do the tea leaves tell us about the public health stories we’ll be paying attention to in 2020? Read on, Dear Reader, read on.
Houston, we’ve got a polio problem
Polio eradication has made STAT’s watch list every year we’ve done these predictions. Earlier predictions have been at least moderately more upbeat. But after 2019, prospects look unsettling.
True, the second of the three poliovirus species — type 3 — was declared eradicated, joining type 2 viruses in the history books. But type 1 stubbornly hangs on in Pakistan and Afghanistan, where the number of children paralyzed in 2019 was more than three times higher than in 2018. In other words, things are going in the wrong direction.
But the really alarming news on the polio eradication front relates to vaccine-derived polioviruses — the weakened but live viruses used in oral polio vaccine that on occasion regain the power to paralyze.
In 2016, type 2 viruses were taken out of the oral vaccine — used mainly in developing countries. It was done in a synchronized withdrawal designed to minimize the risks that type 2 vaccine viruses would continue to circulate and infect the growing cohort of children who weren’t immunized against type 2.
Tragically, the maneuver, called “the switch,” did not go according to plan.
The expectation was that 3 1/2 years after the withdrawal, outbreaks caused by the type 2 vaccine viruses would be dwindling. Instead, they are picking up steam.
At least 17 countries reported finding type 2 vaccine-derived viruses and more than 200 children have been paralyzed by them. Much of the trouble is happening in sub-Saharan Africa, where vaccination campaigns to stop the spread of the vaccine viruses aren’t as aggressive as they need to be and aren’t reaching enough children. A recent report from an independent board that monitors polio eradication termed the situation a crisis.
Much hope is being placed on a new vaccine being developed at warp speed. Also administered orally — a feature that is key to mass vaccination efforts — it contains vaccine viruses that were modified so that they won’t be able to regain their paralytic powers as easily, if at all. So far the data look good, but how well the new vaccine actually works and how likely it is to revert to paralytic form won’t be known until it’s used widely.
If all goes well, it could truly be a silver bullet. But as the Independent Monitoring Board’s report warned, a lot can go wrong with vaccine development and there doesn’t appear to be a plan B. There are lots of white knuckles here. Consider 2020 a pivotal year for polio eradication.
Will cases of the mysterious polio-like ailment spike again?
Public health officials started noticing unusual cases of paralysis, mostly in children, in 2014. The onset was pretty rapid and looked a lot like polio. But polio has been eliminated in the United States. This is something else.
The cause of the paralysis hasn’t yet been proven conclusively, though the current thinking is that viral infections — probably infection with enteroviruses — are responsible. Adding to the mystery surrounding the condition is the fact that since it was first spotted, cases have spiked every two years.
Most of the cases occur in the late summer and early autumn. 2018 was the biggest year so far, with 237 confirmed cases. But 2019 was a low year, with only 32 cases to date. The Centers for Disease Control and Prevention are expecting 2020 will be another big year and are gearing up to be ready.
Disease detectives there hope to make more headway with emergency room physicians and neurologists, to get them to think about notifying public health authorities when they see one of these cases. Infectious diseases doctors are accustomed to contributing to disease surveillance efforts but that’s not typically on the to-do list for neurologists — the specialists who typically assess these patients. As a result, cases may have been undercounted and testing samples definitely have been taken too late in some cases to help solve the mystery.
Whither dengue vaccines?
The world needs effective and safe vaccines to protect against dengue fever, a mosquito-transmitted virus that sickens about 100 million people a year, mostly in Asia, Africa, and Latin America. Its nickname, breakbone fever, gives you a sense of how lousy dengue makes people feel. Most recover, but some go on to have severe and fatal forms of the disease.
Designing a safe dengue vaccine has been scientifically challenging, however. There are four species of the virus — numbered dengue 1 through 4. Infection with one doesn’t protect against infection with the others. In fact, the risk of developing severe dengue is highest during a person’s second dengue infection.
Some scientists have worried a dengue vaccine, if given to children who had never had a bout of dengue, would act like a first infection — leaving them more vulnerable to develop severe disease if they contracted dengue after being vaccinated. (No vaccine is 100% effective.)
There was excitement — and some trepidation — when Sanofi Pasteur was bringing the first dengue vaccine, Dengvaxia, to market. In late 2018, the company disclosed the theorized problem was indeed a concern. When the FDA approved Dengvaxia in 2019, it licensed the vaccine for a tiny sliver of the U.S. market — children aged 9 to 16 living in dengue-endemic parts of the country (there aren’t many) who had already had at least one dengue infection.
2020 should show whether a second vaccine, made by Takeda Pharmaceuticals, can dodge this problem. But data the company presented at a conference in November, which looked at children 18 months after they had been vaccinated, raised red flags.
The company has promised to present data in the first half of the year that will reveal how well the vaccine was working two years after subjects were vaccinated. A lot is at stake here. Another vaccine that can only be used narrowly would be a crushing disappointment.
A third candidate dengue vaccine that was designed at the National Institutes of Allergy and Infectious Diseases and licensed to Brazil’s Butantan Institute is also in testing in Brazil, where a Phase 3 trial began in early 2016.
Might there be preliminary data from this trial in 2020? Alexander Precioso, director of Butantan’s division of clinical trials and pharmacovigilance, won’t say. “We have not yet publicly disclosed timelines,” he told STAT.
We peeked at the trial’s listing on ClinicalTrials.gov, the registry run by the National Library of Medicine. It projects that the final data collection date for the primary outcome measure is June 2020 — though whether that is up to date, we cannot say.
So perhaps 2020 will reveal critical data from testing of two dengue vaccines. Cross your fingers and toes, Dear Reader. Effective dengue vaccines that can be safely used across a range of ages and in people who have never had dengue before would make 2020 a banner year indeed.