Infants are vulnerable to chickenpox earlier than previously thought, study finds

Infants are not protected against varicella-zoster virus, the virus that causes chickenpox, for several months before they are eligible for vaccination, a new study suggests.

In some cases, infants may be at risk of infection as early as one month after birth.

“Antibodies transferred via the placenta during pregnancy protect babies against many infectious diseases at birth, including the chickenpox virus,” explains Associate Professor Shelly Bolotin, director of the Center for Vaccine Preventable Diseases (CVPD). from the University of Toronto at the Dalla Lana School. of Public Health and first author of the study.

“However, our research has found that this protection wears off quickly, leaving infants vulnerable to infection for several months before they are eligible for the chickenpox vaccine, which in Ontario is given at 15 months of age. ”

Using samples collected at the Hospital for Sick Children (SickKids) in Toronto, researchers examined antibody levels in blood samples from 187 infants aged less than one year. They found that antibodies protecting against chickenpox disappeared quickly and that almost 80 percent of infants were likely to be infected before the age of three months. At six months, all infants studied were susceptible to chickenpox.

The results, published in the journal PLOS Oneconcur with previous research indicating that the level of antibodies babies receive from their mothers at birth fades quickly.

“Although many people consider chickenpox to be a mild infection in children, and this is usually the case, it can lead to complications such as skin infections, pneumonia or inflammation of the brain, especially in young people. children,” explains Michelle Science, lead author of the study and member of the CVPD. infectious disease consultant and medical advisor for infection prevention and control at SickKids.

Science, who is also an assistant professor at the Temerty Faculty of Medicine, notes that infants are at higher risk of complications than older children and are the age group most likely to be hospitalized. Before the vaccine was available, Canada recorded approximately 350,000 cases of chickenpox per year and 1,500 people hospitalized each year.

The chickenpox vaccine helps protect individuals against infection as well as serious complications that may occur. Getting vaccinated also helps reduce the number of cases of chickenpox in all age groups in a community, even in people who are too young or too old to be vaccinated.

The chickenpox vaccine is already part of routine childhood immunization in several countries, including Canada, Australia, Germany and the United States. In the United Kingdom, the Joint Committee on Vaccination and Immunization recently recommended that a chickenpox vaccination program be introduced into the routine childhood immunization schedule and that a catch-up program for older children be also implemented in the future.

“The results of our study confirm that everyone around an infant should be protected against chickenpox, either because they have already been infected or through vaccination,” explains Science.

She adds that these findings may be helpful to both parents and health care providers, who should think of chickenpox whenever they see a rash, even in a young baby, and when evaluating the risk of infection of an infant if exposed to a case.

Bolotin and his co-authors noted that more research is needed on varying demographics and whether factors such as breastfeeding or mother’s age influence their baby’s antibody levels.

In the meantime, this study reminds us of the importance of vaccinations.

“Vaccination isn’t just about protecting yourself, it’s also about protecting your family, friends and neighbors,” says Bolotin. “Our study further confirms how getting vaccinated can protect some of the most vulnerable – and in this case, newest – members of our society.”