Congenital cytomegalovirus cases declined significantly during the COVID-19 pandemic, compared with a period before the pandemic, based on data from nearly 20,000 newborns.
A study originated to explore racial and ethnic differences in congenital cytomegalovirus (cCMV) began in 2016, but was halted in April 2020 because of the COVID-19 pandemic, wrote Mark R. Schleiss, MD, of the University of Minnesota, Minneapolis, and colleagues. The study resumed for a period from August 2020 to December 2021, and the researchers compared data on cCMV before and during the pandemic. The prepandemic period included data from April 2016 to March 2020.
“We have been screening for congenital CMV infection in Minnesota for 6 years as a part of a multicenter collaborative study that I lead as the primary investigator,” Dr. Schleiss said in an interview. “Our efforts have contributed to the decision, vetted through the Minnesota Legislature and signed into law in 2021 (the “Vivian Act”), to begin universal screening for all newborns in Minnesota in 2023. In the context of this ongoing screening/surveillance study, it was important and scientifically very interesting to examine the impact of the COVID-19 pandemic on the risk of congenital CMV infection,” he explained.
The findings were published in a research letter in. A total of 15,697 newborns were screened before the pandemic and 4,222 were screened during the pandemic period at six hospitals. The majority of the mothers participating during the prepandemic and pandemic periods were non-Hispanic White (71% and 60%, respectively).
Overall, the percentage screened prevalence for cCMV was 79% in the prepandemic period and 21% during the pandemic, with rates of 4.5 per 1,000 and 1.4 per 1,000, respectively.
Although the highest percentage of cCMV cases occurred in newborns of mothers aged 25 years and older (86%), the prevalence was highest among newborns of mothers aged 24 years and younger (6.0 per 1,000). The prevalence of cCMV overall was higher in infants of non-Hispanic Black mothers vs. non-Hispanic White mothers, but not significantly different (5.1 per 1,000 vs. 4.6 per 1,000) and among second newborns vs. first newborns (6.0 vs. 3.2 per 1,000, respectively).
Factors related to COVID-19, including reduced day care attendance, behavioral changes, and mitigation measures at childcare facilities such as smaller classes and increased hand hygiene and disinfection may have contributed to this decrease in cCMV in the pandemic period, the researchers wrote in their discussion.
The comparable prevalence in newborns of non-Hispanic Black and White mothers contrasts with previous studies showing a higher prevalence in children of non-Hispanic Black mothers, the researchers noted in their discussion.
The study was limited by several factors, including the variation in time points for enrollment at different sites and the exclusion of families in the newborn nursery with positive COVID-19 results during the pandemic, they wrote. More research is needed on the potential effects of behavioral interventions to reduce CMV risk during pregnancy, as well as future CMV vaccination for childbearing-aged women and young children, they concluded.
However, the researchers were surprised by the impact of COVID-19 on the prevalence of cCMV, Dr. Schleiss said in an interview. “We have had the knowledge for many years that CMV infections in young women are commonly acquired through interactions with their toddlers. These interactions – sharing food, wiping drool and nasal discharge from the toddler’s nose, changing diapers, kissing the child on the mouth – can transmit CMV,” he said. In addition, toddlers may acquire CMV from group day care; the child then sheds CMV and transmits the virus to their pregnant mother, who then transmits the virus across the placenta, leading to cCMV infection in the newborn, Dr. Schleiss explained.
Although the researchers expected a decrease in CMV in the wake of closures of group day care, increased home schooling, decreased interactions among children, hygienic precautions, and social isolation, the decrease exceeded their expectations, said Dr. Schleiss. “Our previous work showed that in the 5-year period leading up to the pandemic, about one baby in every 200 births was born with CMV. Between August 2020 and December 2021, the number decreased to one baby in every 1,000 births,” a difference he and his team found striking.
The message from the study is that CMV can be prevented, said Dr. Schleiss. “Hygienic precautions during pregnancy had a big impact. Since congenital CMV infection is the most common congenital infection in the United States, and probably globally, that causes disabilities in children, the implications are highly significant,” he said. “The hygienic precautions we all have engaged in during the pandemic, such as masking, handwashing, and infection prevention behaviors, were almost certainly responsible for the reduction in CMV transmission, which in turn protected mothers and newborns from the potentially devastating effects of the CMV virus,” he noted.
Looking ahead, “Vaccines are moving forward in clinical trials that aim to confer immunity on young women of childbearing age to protect future pregnancies against transmission of CMV to the newborn infant; it would be very important to examine in future studies whether hygienic precautions would have the same impact as a potential vaccine,” Dr. Schleiss said. More research is needed to examine the effect of education of women about CMV transmission, he added. “We think it is very important to share this knowledge from our study with the pediatric community, since pediatricians can be important in counseling women about future pregnancies and the risks of CMV acquisition and transmission,” he noted.