HERE’s a worrying statistic: We’re just a few months into 2021, and in the UK, public-health authorities have yet to detect any cases of flu. The reason, experts believe, is that the mask wearing, social distancing and lockdowns designed to slow the spread of coronavirus have essentially wiped out the flu virus. Flu numbers are down all over the world.
This is good news, of course. So why is it also worrying? If these measures have also kept the flu at bay, they may have kept other infectious agents under control as well, including some that are far more dangerous. And when we emerge from the COVID crisis and start to relax public-health measures — in particular, allowing international air travel to resume — these more dangerous agents could surprise us with a violent resurgence.
Of greatest concern is one particular virus, Measles morbillivirus. In 1980, a measles outbreak killed some 2.6 million people worldwide, slightly more than the global death toll so far from SARS-CoV-2. By 2014, vaccinations had brought yearly deaths down to 100,000, but faltering vaccine coverage in recent years has allowed numbers to surge, and scientists worry that the disruption to measles vaccinations, including cancellations, during the current pandemic mean that measles may be set for a massive global outbreak just as the world wakes from the COVID nightmare.
The measles vaccine is composed of two doses — known as MCV1 and MCV2 — and the vaccination rate needs to be above 95% with both doses to prevent outbreaks. Unfortunately, MCV1 coverage has been stuck at around 85% for more than a decade, and MCV2 coverage, while rising, is still only at 71%. This is why, after measles cases fell steadily from 2010 to 2016, numbers again began growing — reaching 89,000, 109,000, 142,000 and 207,000 deaths in the following years.
We don’t yet know about 2020, as there’s a delay of nine or 10 months before the World Health Organization can collect and report measles case data. Presumably, however, numbers may be improved precisely because of the measures deployed against the COVID pandemic. But it’s what happens after COVID that’s concerning.
During the first six months of the coronavirus pandemic, some 50 countries canceled mass vaccination campaigns for various viruses. Routine immunizations were also disrupted by issues such as lack of public transport, with millions of children missing out on important vaccinations. This is like priming an explosive: Vaccination is our primary measure against viruses such as the measles, which is a fierce infectious agent. The reproductive number for the new coronavirus — the number of further infections resulting from any one new infection — is between 2 and 3. The number for measles is 12 to 18, making it one of the world’s most contagious known viruses.
Other consequences of the COVID pandemic make conditions ripe for a huge measles outbreak, according to David Durrheim, a professor of public health at the University of Newcastle in Australia. “Children may also be more vulnerable due to other pandemic impacts, such as disruptions to food supply,” he wrote in an e-mail. “Malnourished children are considerably more vulnerable to measles complications and death.”
With measles, of course, we’re not as vulnerable as we were last spring when we faced a novel coronavirus. After all, we’ve had effective measles vaccines for decades, and the measles virus mutates so slowly that it can’t evolve to defeat them. The challenge is how to achieve sufficient vaccine coverage, hard enough in normal times, and now extra-hard given all the vaccinations missed in the past year. While the problem is more acute in developing nations, it still affects the US and other developed nations. It’s imperative, as Durrheim and other medical specialists recently argued, that countries put an emphasis on “catch-up” measles vaccinations, even as they roll out COVID vaccines.
The deadline is tight given the looming return of international air travel, which could happen faster than we think. Unless governments around the world act quickly, we could face a tragic paradox, as the end of the historic COVID pandemic could set in motion another pandemic with comparable consequences.