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COVID questions: Vaccines for toddlers; making sense of metrics

May 12, 2022 By Kristina LeVan

This ongoing series answers questions about COVID-19 and the pandemic. If you have a question to submit, please email it to covid19update@uc.wisc.eduSee answers to previous COVID questions, and visit our COVID-19 impact site.

Q. We have two kids under the age of five and are eagerly waiting on news of the vaccine for that age group. Am I wrong in thinking that it is taking longer to approve the vaccine for them? What factors might be holding up FDA approval of the COVID-19 vaccine for children under five—are there any updates on the progress? 

The studies on pediatric vaccines did not start until quite some time after the adult studies began (and actually only when the initial phases of adult studies were completed).  Until there was clear safety and efficacy data in adults, none of the pharmaceutical manufacturers were comfortable beginning experiments in children nor were approved by FDA to move forward.

Once they did begin, they first had to identify the appropriate doses, before then enrolling larger numbers of children.  These studies then require long term follow-up to help determine the duration of protection and safety of the vaccines, in particular in the setting of the changes in the circulating SARS-CoV2 viruses.  As you probably heard in the news back in Feb 2022, the original Pfizer studies using 2-doses of a dose at 1/10th of the adult doses did not provide sufficient immunity, and so they have been performing additional studies with a 3rd dose since then.  Both Moderna and Pfizer are starting to submit their study data to FDA for review over the next month or so, and we expect review to be completed this summer.

— James Conway, Pediatric Infectious Diseases Fellowship Program Director and School of Medicine and Public Health Office of Global Health Director

What information is the most important on Covid dashboards at this phase of the pandemic? Should I care about numbers of cases, or is it more important to look at hospitalizations? How should I make sense of percent positivity given that fewer people are testing by PCR?

Focus on trends rather than absolute numbers. Throughout the pandemic, the number of confirmed cases on a given day has never been representative of all transmission occurring in the community. That bias cancels out when examining the change in daily cases over short periods of time. If cases and percent positivity are trending upward week after week, it’s a good reminder that the pandemic is not over, and the situation is worsening. The absolute number of hospitalizations tells us that there are many people in our community who are vulnerable to experiencing severe COVID.

Reported as low, medium, or high, the COVID-19 Community Level from the CDC considers hospital beds being used, hospital admissions, and the total number of new COVID-19 cases in an area. However, this is a “living with COVID” metric to prevent things from getting out of control. It is not a metric to tell us that we ought to prevent COVID transmission to begin with. Given that more than half of new infections are acquired from someone who did not have symptoms and was likely unaware that they were infectious, it’s a good idea for everyone to be as vigilant as possible to avoid getting sick.

— Ajay Sethi, Associate Professor of Population Health Sciences

See more answers to COVID questions at Also, visit our COVID-19 impact site.