Millions of children around the world, most of them in the poorest countries, missed some or all of their childhood vaccinations over the past two years because of a combination of conflicts, climate emergencies, misinformation campaigns, pandemic lockdowns and Covid vaccination efforts that diverted resources, according to a new analysis from Unicef, the United Nations agency that vaccinates half the world’s children, and the World Health Organization.
It is the largest backslide in routine immunization in 30 years, the report said. Combined with rapidly rising rates of malnutrition, it has created conditions that could threaten the lives of millions of young children.
“This is an emergency for children’s health — we have to think about the immediate stakes, the number of children that are going to die because of this,” said Lily Caprani, head of advocacy for Unicef. “It’s not in a few years’ time; it’s quite soon.”
The percentage of children worldwide who had received three doses of the vaccine against diphtheria, tetanus and pertussis, known as DTP3 — which Unicef uses as a benchmark for immunization coverage — fell five points between 2019 and 2021, to 81 percent. Measles vaccination rates also fell to 81 percent, and polio coverage dropped significantly, too. A vaccination coverage rate of 94 percent is necessary for herd immunity, to interrupt the chain of transmission of a disease.
This translates to 25 million children who did not receive a basic intervention to protect against lethal illnesses.
The number of what Unicef calls zero-dose children — those who have not received a single dose of the most basic vaccines — increased sharply during the pandemic, to 18 million from 13 million in 2019. This group includes half of all children who die before age 5.
The agency had been hoping that after a sharp decline in 2020 that was driven by lockdowns, school closures and other Covid response measures, childhood vaccination coverage would rebound in 2021, said Dr. Niklas Danielsson, Unicef’s Nairobi-based senior immunization specialist.
But instead, the problem got worse. DTP3 and measles coverage are at the lowest level since 2008, the report found.
Dr. Danielsson said the rate of vaccination coverage in 2021 matched that of 2008. “But since then, the birth cohorts have increased, which means that the number of children who do not complete vaccinations, or do not even start, is the largest in the last 30 years,” he said.
He and many others in the child immunization field had anticipated a recovery last year as health systems learned to adapt to the demands of the pandemic. Instead, misinformation campaigns about Covid vaccination, and broader mistrust of governments over public health measures, spilled over to deter routine immunization, he said.
At the same time, health systems in the poorest countries scrambled to carry out limited Covid vaccination, diverting critical access to freezers and the health workers to put shots in arms.
The world made sustained progress on childhood vaccination coverage through the 1990s and the first decade of this century. Rates then began to plateau, because the remaining children were the hardest to reach, such as those in active war zones or in nomadic communities. But before the pandemic, there had been a redoubled commitment, with support from organizations like the Bill and Melinda Gates Foundation and Gavi, the global vaccine alliance, to try to reach the remaining pockets of zero-dose children. Covid has pulled away much of that attention and investment.
Over the last two years, India, Nigeria, Indonesia, Ethiopia and the Philippines recorded the highest numbers of children who had missed out on vaccines.
Brazil was also on the list of the 10 most-affected countries, a harsh shift for a country once renowned for its high vaccination coverage rates. About 26 percent of Brazilian infants had received no vaccines in 2021, compared with 13 percent in 2018.
“The work of 30 years has been lost overnight,” said Dr. Carla Domingues, an epidemiologist and former coordinator of Brazil’s national immunization program.
Vaccination became a politicized subject in Brazil during the Covid pandemic, she said. The federal government, led by President Jair Bolsonaro, downplayed the significance of the coronavirus even as Brazil had one of the world’s highest death rates and said he would not get his own 11-year-old vaccinated against the virus.
“For the first time, the federal government was not recommending a vaccine, and it created a whole environment of doubt that had never existed in Brazil, where vaccination was totally accepted,” Dr. Domingues said.
At the same time, anti-vaccination groups that had not had much purchase in Brazil moved into the country during the pandemic, she said, and began circulating misinformation in Portuguese on social media.
And all of this was happening, Dr. Domingues said, at a time when Brazilians were a generation removed from the serious illnesses they were being urged to vaccinate their children against, leading them to question the necessity.
“Parents don’t know the impact of measles, or of polio, so they start to pick and choose vaccinations,” she said. Data showing that acceptance of the pneumonia vaccine is higher than that for polio makes that clear. “Parents are choosing not to do polio. They say, ‘It’s been 30 years with no polio, so do I need to do this?’”
And yet they have a clear sign of the risk, she said: A handful of measles cases were found earlier this year in São Paulo, six years after Brazil had reported eradicating the disease. “Measles is now circulating — that gives us a concrete example of what could happen with diphtheria, meningitis and so many other diseases,” she said.
In the Philippines, 43 percent of infants had not had any vaccinations last year. There, the problem lies partly in tough Covid public health measures, including lockdowns. “If you are not allowed to take your children out apart from certain hours of the day, if they can’t go to school, if living costs are increasing, going to a health enter to have your child vaccinated drops down on your priorities,” Dr. Danielsson said.
But the Philippines’ situation is also complicated by lingering mistrust of vaccination after a wide rollout of a dengue vaccine in 2016 that later proved to have caused more severe cases of the disease in some who had received it.
Ms. Caprani of Unicef said an extraordinary amount of resources and commitment would be needed to bring vaccine levels back up to where they had been.
“It’s not going to be enough to just go back to business as usual and restore ordinary, routine immunization,” she said. “We’re going to need really concerted investment and catch-up campaigns, because there’s a growing cohort of millions of children who are completely unimmunized living in countries that have high levels of malnutrition and other stresses.”
In Zimbabwe, for example, there is currently a measles outbreak in which one in 10 children hospitalized with the illness is dying. (The typical mortality rates are one in 100 in low-income countries and below one in 1,000 in high-income nations.)
Dr. Fabien Diomande, a polio eradication expert with the Task Force for Global Health who worked for years on polio campaigns in West and Central Africa, said reversing the decline in childhood immunization would require new nimbleness, innovation and resources.
“It’s like we’re in a new world — those emergencies are not going to disappear,” he said. “We will still have Covid. We will still have climate crises. We have to learn how to work in the context of multiple public health emergencies.”
Dr. Domingues in Brazil said that Covid vaccination efforts could offer some lessons for how to catch up. Brazil achieved high vaccination coverage by providing pop-up vaccination posts and making shots available at night and on weekends.
Ms. Caprani said that while there was a heartening renewed interest in global health cooperation because of Covid, investment in new surveillance measures and other novelties risked distracting from the simple intervention needed to address the child immunization crisis: deployment of thousands of community health workers.
“We aren’t going to solve this with poster campaigns or social media posts,” she said. “You need outreach by reliable, well-trained, properly compensated community health workers who are out there day in, day out, building trust — the kind of trust that means you listen to them about vaccines. And there simply aren’t enough of them.”
Jason Gutierrez contributed reporting from Manila.