A new report released by UNICEF finds that 67 million children across the world missed out on either some or all routine vaccinations between 2019 and 2021, and 48 million children didn't receive a single dose during this time period.

"We've seen the largest sustained decline in the number of children reached with their basic childhood immunizations," says Lily Caprani, chief of global advocacy at UNICEF.

"And the consequences of that will be measured in children's lives. It's the largest continuous decline in childhood vaccinations in 30 years."

But preliminary data from 2022 (not included in the report) suggests some encouraging signs of an uptick in vaccinations in the past year.

The unvaccinated children born just before the COVID-19 pandemic, or during it, are now 3 years old — approaching the age when they would have received these vaccines, typically Hepatitis B, polio, measles, rotavirus, diphtheria, tetanus and pertussis. So these kids are "completely unprotected," says Caprani.

The cost of COVID

It's a reflection of how the pandemic disrupted basic health services, says Brian Keeley, editor-in-chief of UNICEF's annual report, State of the World's Children.

"Clinics were closed," says Keeley. "Families were on lockdown, they may not [have] been able to travel or they may not have been willing to travel because of fear of visiting a health facility during a pandemic."

And countries had to make tough choices about how best to prioritize funds and health resources, he adds. In some cases, that resulted in "resources being diverted to treat people who were sick with COVID or provide emergency services.

"We saw that hospitals, the health facilities were overloaded with COVID cases," says Dr. Malalay Ahmadzai, chief of health and nutrition at UNICEF's office in the Philippines. "In the meantime, the resources also had to be shifted to address the needs of hospitals in terms of the equipment, in terms of the testing capacity and all that."

Routine health services for women, children and adolescents were disrupted as a result, she adds, including childhood immunizations.

Countries in Africa and South Asia have the highest number of under-vaccinated kids and those with zero doses. The totals in West and Central Africa come to 6.8 million children. India leads the world with the largest number of children with zero doses – 2.7 million – followed by Nigeria with 2.2 million unvaccinated children.

"This is really a crisis within a crisis," says Kate O'Brien, director of the Department of Immunization, Vaccines and Biologicals at the World Health Organization.

"The backsliding of the immunization program is a direct result of the pandemic, and it should be responded to with the same urgency as we have to the pandemic."

That's because many countries are already seeing rising cases of the infectious diseases that these childhood vaccines protect against.

"We're seeing a pretty unprecedented number of measles outbreaks," says O'Brien.

Last year, 33 countries reported "large or disruptive cases of measles," he says. "That's compared to 22 countries in the previous year."

And the total number of measles cases doubled from 2021 to 2022, says Keeley, with major outbreaks in India, Somalia, Nigeria, Afghanistan and Ethiopia.

Measles usually results in a high fever followed by a rash. The disease can cause serious complications, like blindness, encephalitis, severe diarrhea, dehydration and pneumonia. According to the WHO, there were almost 10 million cases of measles around the world in 2018, and more than 140,000 individuals died. Most were children under the age of 5.

Diseases as infectious as measles can spread quickly in communities, says Caprani.

"So it can very quickly put great strain on health-care providers trying to treat the consequences of the illness in a very vulnerable population," she says.

Polio cases also saw a troubling trend, says Keeley.

"When you look at the numbers for 2022, the number of children paralyzed by polio was up 60% [compared to] the previous year," he says. Some 800 cases were reported.

"For my generation, we thought [polio] was over. We thought it was dealt with. It isn't. If we don't keep up efforts to vaccinate every child, this will come back."

There have also been outbreaks of yellow fever in 15 countries, says O'Brien. "This is an increased number of countries," she says. "Some of these countries are countries that in the past had actually conducted preventive vaccine campaigns" for youngsters.

UNICEF estimates at least 200,000 lives have been lost due to these disruptions in childhood vaccinations, says Caprani.

"All of the diseases we're talking about that are vaccine preventable, the more you miss children in that community, the more the entire community and wider society is then vulnerable to a public health emergency," she adds.

The WHO's O'Brien is hopeful that many countries managed to get back on track with childhood vaccinations in 2022. At least that's what preliminary data from 72 countries suggests, she says.

"So based on those countries, it looks like we've gotten back to roughly a 2019 level, possibly with some improvement."

One good example is India.

The country had "a strong commitment" to the immunization program, she says. A program called Mission Indradhanush targeted parts of the country where zero-dose children live.

"We know that in 2022 they've had a very good recovery of their program and are really a global leader in this area," adds O'Brien.

Keeley says UNICEF is currently analyzing vaccination data for 2022 and will have a clearer picture to report later this summer.

Losing faith in vaccines

But the new UNICEF report finds another troubling trend that will need to be addressed by public health programs – a decline in people's perception of the importance of vaccines.

Of the 55 countries surveyed, 52 showed a decline in vaccine confidence. The remaining three — China, India and Mexico — saw a rise in vaccine confidence.

"Given the context of backsliding and escalating outbreaks, we're really concerned," says Caprani.

There's been a rise in misinformation about vaccines during the pandemic, she says, and that needs to be tackled both by social media platforms and health-care providers.

"At the country level," adds Caprani, "it's very important that parents, families and communities have access to reliable, strong, evidence-based information about the risks of illnesses like measles, polio, diphtheria, and about the benefits of vaccines."