One in a series of stories looking back at some of our top stories.

At the beginning of 2022, the Pennsylvania Department of Health was reporting upwards of 15,000 new cases of COVID-19 a day. By December, the department was reporting data only once a week, and “15,000 new cases” became the average number of new cases per week.

Dr. Maureen Lichtveld, dean of the University of Pittsburgh School of Public Health, said several factors have influenced the decline in reported COVID cases. These factors include the availability of at-home tests — the results of which were not reported to the state but at least helped prevent the spread of the illness when people with a positive result stayed home — and the rise in the number of people who got vaccinated against the disease over the year.

The virus has continued to infect people, however. Lichtveld said this is the result of developing variants of COVID-19 which have infected people regardless of vaccination status.

She said the herd immunity, which occurs when a large portion of a community becomes immune to a disease, has yet to occur in the nation and Pennsylvania because the population has not reached the necessary rate of vaccination to protect against the spread of COVID.

“When other variants are circulating, we'll create an annual vaccine rather than continuing to boost,” Lichtveld said. “The reason why we were successful is because we were fairly quick with the federal government and state governments in getting vaccines.

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