Large outbreaks of diseases killing mostly children are spreading around the world, a grim legacy of disruptions to health systems during the Covid-19 pandemic that left more than 60 million children without a single dose of standard vaccines received for children.

As of the middle of this year, 47 countries reported major measles outbreaks, compared to 16 countries in June 2020. Nigeria is currently facing the largest diphtheria outbreak in its history, with more than 17,000 suspected cases and nearly 600 deaths so far. Twelve countries, from Afghanistan to Zimbabwe, report circulating poliovirus.

Many of the children who missed their vaccinations have now outgrown routine vaccination programs. So-called “zero dose children” They are responsible for almost half of all child deaths from vaccine-preventable diseasessaid Gavi, the organization that funds vaccinations in low- and middle-income countries.

Another 85 million children are underimmunized as a result of the pandemic – meaning they have received only a portion of the standard, multiple-shot vaccination regimen needed to be fully protected against a particular disease.

The cost of not reaching these children is becoming increasingly clear. According to the data, deaths from measles increased by 43 percent in 2022 compared to the previous year (to 136,200). a new report by the World Health Organization and the Centers for Disease Control and Prevention. This is what the numbers for 2023 show the sum could be twice as high.

“The decline in vaccination coverage during the Covid-19 pandemic has led us directly to this situation of rising illnesses and deaths among children,” said Ephrem Lemango, deputy director for immunization at UNICEF, which provides vaccines to almost half of all children each year supporting children around the world. “With each new outbreak, the burden on vulnerable communities increases. We must act quickly now and make the necessary investments to catch up with the children who have been missing during the pandemic.”

One of the biggest challenges is that the children who missed their first vaccination between 2020 and 2022 are now older than the age group usually routinely observed in primary health centers and in normal vaccination programs. Reaching them and protecting them from diseases that can easily kill in countries with the weakest health systems requires additional efforts and new investments.

“If you were born within a certain period of time, you were missing, period, and you won’t be caught just by restoring normal services,” said Lily Caprani, UNICEF’s chief of global advocacy.

UNICEF is asking Gavi for $350 million to purchase vaccines to reach these children. Gavi’s board will consider the application next month.

Unicef ​​is urging countries to implement catch-up vaccination, an extraordinary, one-off program to reach all children between the ages of 1 and 4 who have been missing.

Many developing countries have some experience with conducting measles catch-up campaigns targeting children ages 1 to 5 or even 1 to 15 in response to outbreaks. But now those countries must also deliver the other vaccines, train staff — typically community health workers who are only familiar with vaccinating babies — and procure and distribute the actual vaccines.

Dr. Lemango said that despite the urgency of the situation, it had been difficult to put together plans for such campaigns and that he hoped most could come together in 2024.

“After the pandemic, there was this hangover – no one wanted to campaign,” he said. “Everyone wants to return to normality and increase immunization regularly. But we already had unfinished business.”

In some countries, such as Brazil, Mexico and Indonesia, health systems have recovered from the severe disruptions caused by Covid-19 and have returned to or even exceeded the vaccination rates they achieved before the pandemic. But others – mostly countries where vaccination rates were already well below targets set by UNICEF – have not reached their previously lower levels.

The countries with the most zero-dose children include Nigeria, Ethiopia, India, the Democratic Republic of Congo and Pakistan. Many people with the lowest insurance coverage face increasing challenges, such as the civil wars in Syria, Ethiopia and Yemen; the growing number of climate refugees in Chad; and both problems in Sudan.

Ghana’s experience is representative of the challenges faced by many low-income countries. Parents were unable to take their children for routine vaccinations when communities were locked down to protect against Covid, and when those restrictions were lifted, many parents still stayed away for fear of infection, said Priscilla Obiri, a community nurse in charge of vaccinations in low-income fishing communities on the outskirts of the capital Accra.

Of the children Ms. Obiri sees these days at a typical pop-up vaccination clinic, where she sets up a table and a few chairs in the shade at an intersection, up to a third have incomplete or sometimes no vaccinations, she said. She agrees with her mothers on a plan to close the gap.

But some parents don’t or can’t take their children to a clinic. “We need to go out into the community and look for them,” she said.

As Ms. Obiri and her colleagues try to regain this lost ground, they face another challenge: disinformation campaigns and hesitancy about Covid vaccines have expanded, undermining some of the traditional eagerness that parents had to routinely vaccinate their children, so the Vaccine Confidence Project, a long-standing research initiative at the London School of Hygiene and Tropical Medicine.

“In 55 countries, between 2015 and 2022, there was a steep decline in the number of people saying that routine vaccinations for children are important,” said the project’s leader, Heidi Larson, whose team collected “robust global survey data,” as she said it was named in more than 100 nationally representative surveys.

Even as people around the world search for information about vaccines, there has been a rise in misinformation and disinformation, she said, and people with low trust in officials and official guidance are particularly vulnerable to believing alternative sources of information.

Dr. Kwame Amponsah-Achiano, who leads Ghana’s child immunization program, said he does not believe confidence has fallen during the Covid pandemic. Demand remains high and in some areas exceeds the program’s ability to deliver, he said.

Ms. Caprani said UNICEF found that both issues were occurring in parallel.

“Demand is outstripping not only physical supply, but also access – convenient, affordable, accessible access – and at the same time trust is falling,” she said. “They’re not necessarily the same people.”

Last year, 22 million children missed the routine measles vaccination in the first year of life – 2.7 million more than in 2019 – while another 13.3 million did not receive their second vaccination. To achieve herd immunity and prevent outbreaks, 95 percent of children must receive both doses. Measles acts as an early warning system for vaccination gaps because it is highly transmissible.

“There are communities where a measles outbreak is a bad thing, and there are communities where it is a death sentence due to the combination of other risk factors such as poor malnutrition, poor access to health care and poor access to clean water,” Ms. Caprani said.