Immunology, Medical News, Pediatrics, World health

Scientists expect surge in RSV in young children due to pandemic lockdowns

Children may be more susceptible to RSV since most pregnant women and babies did not develop immunity during the previous season.

As COVID-19 cases have declined and public health measures brought on by the pandemic have been lifted, cases of respiratory syncytial virus (RSV) have risen rapidly in Australia and, more recently, the United States. The respiratory syncytial virus is a virus that infects the lower respiratory system and can lead to serious illness and death.

Respiratory syncytial virus (RSV) is a common respiratory virus that typically causes mild, cold-like symptoms. The virus is not typically dangerous among healthy adults, as most recover in a week or two. However, RSV has a much more serious prognosis in young children and newborns younger than 1 year of age. It is the most common cause of bronchiolitis (inflammation of the small airways in the lung) and pneumonia (infection of the lungs) within this age group. 

Canada, like other nations, saw extremely few cases of RSV during the COVID-19 pandemic, with only 239 positive cases between the dates of August 29, 2020, and May 8, 2021, compared to 18,860 positive tests in the same time the previous year (between August 25, 2019, and May 2, 2020). Over the last year, the infection seemed to vanish.

However, a spike in RSV infections in Canada this summer, as well as in other countries, may put a strain on health-care resources in pediatric intensive care units (ICUs). Because most pregnant women and newborns did not establish immunity during the previous season, children may be more susceptible to disease this year.

Dr. Pascal Lavoie, BC Children’s Hospital Research Institute and the University of British Columbia, Vancouver, BC, and coauthors write, “The off-season comeback in seasonal respiratory viruses now potentially poses a threat to vulnerable infants.”

RSV infected approximately 2.7 million children worldwide annually before the onset of the COVID-19 pandemic, and it was the fourth leading cause of death in young children. Experts have not commented whether immunity from the COVID-19 virus translates to a healthier immune response against RSV. Despite both viruses causing similar symptoms among infected individuals, they are entirely unique in their composition and how they attack the body. 

The return of RSV infections in Australia and the United States emphasizes the role of population immunity in controlling RSV epidemics after peak exposure. Studies have shown that maternally derived antibody levels fluctuate cyclically, with a spike during the RSV winter season and a reduction throughout the summer months. Due to lifelong seasonal exposure to the virus and memory B- and T-cell immunity, most afflicted adults younger than 65 years remain asymptomatic or have moderate sickness during RSV seasons. Immunologically naive infants, on the other hand, rely on passively transferred maternal antibodies to protect them after birth, but these antibodies fail to prove effective after 6 months.

Experts recommend continuing to emphasize handwashing and basic hygiene measures, as well as other protective measures, continued testing for RSV when in applicable situations, planning by pediatric ICUs to manage an increase in severe RSV cases, and administering preventive treatment to high-risk infants in the summer before the upcoming flu season.

“Respiratory syncytial virus programs should prepare to administer immunoprophylaxis off season, to the highest-risk infants, if cases increase to levels that normally trigger the fall season start,” says Lavoie and colleagues. 


The study was published in Canadian Medical Association Journal, on July 26th, 2021.

Abstract. Australia and, more recently, the United States have seen a resurgence of cases of respiratory syncytial virus (RSV) infection in the summer season, as COVID-19 pandemic–related physical distancing measures are being relaxed. We argue that Canada should anticipate a similar resurgence in seasonal respiratory viruses in the summer of 2021. It is crucial that we continue to monitor respiratory illnesses to inform RSV prevention programs and help protect vulnerable patients. This may involve administering RSV monoclonal antibody therapy in high-risk children off season, which is a major departure from standard practice.


Pascal M. Lavoie, Frederic Reicherz, Alfonso Solimano and Joanne M. Langley; CMAJ July 26, 2021 193 (29) E1140-E1141; DOI: https://doi.org/10.1503/cmaj.210919

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