Nationally and globally, there are signs that the pandemic has opened up new vulnerabilities to diseases long in retreat. Routine immunizations have been hindered by a host of obstacles, including COVID-19-related lockdowns and growing vaccine resistance stoked by misinformation and politicization. A recent analysis by UNICEF and the World Health Organization showed that the percentage of children worldwide who received all three doses of the vaccine against diphtheria, tetanus and pertussis — a measure of overall immunization — dropped 5 points between 2019 and 2021 and that measles and polio vaccinations fell, too. The organizations say that’s the largest sustained decline in childhood vaccinations in the roughly 30 years they’ve been collecting data.

That could create greater risk of polio, a scourge of the first half of the 20th century in the U.S. Highly contagious and potentially life-threatening, polio historically has victimized mostly young children, attacking their spinal cords, brain stems or both.

The virus spreads when fecal material or respiratory droplets from infected people get into water or food or onto other people’s hands, which they then put into their mouths. This may sound unusual, but it’s among the more common ways viruses circulate, especially among children.