Vaccine in mothers protects babies from bronchiolitis up to 6 months – 05/15/2023 – Health

Vaccination of women with a gestational age of 24 to 36 weeks against RSV (respiratory syncytial virus) offered protection of 81.8% to babies up to three months of age from serious infection requiring hospitalization for the virus.

Protection had a slight drop after six months of age, going to 69.4%, but still a level considered good to prevent infection requiring hospitalization.

Regarding respiratory disease that was not considered serious, the vaccine offered protection of 57.1% in the first three months (90 days) of the babies’ lives, but this value was not statistically significant. At six months of age (180 days), however, the protection conferred was 51.3%.

The occurrence of immunization side effects up to one month after application was 13.8% in women and around 37.1% in babies, and they were well tolerated.

The results are from a randomized, double-blind, placebo-controlled clinical trial in phase 3 (the last step before approval by regulatory agencies) with 7,392 pregnant women from 18 countries that evaluated the effectiveness of a single dose of vaccine in protecting against infections of RSV in infants.

RSV is known to cause bronchiolitis in children up to two years of age and has a high lethality in babies up to six months of age, especially premature infants.

There is currently no licensed vaccine that protects against RSV in this age group. Recently, the US agency FDA (Food and Drugs Administration) approved the first vaccine against bronchiolitis in the world, produced by the pharmaceutical company GSK and recommended for the elderly.

The study tested a vaccine produced by pharmaceutical company Pfizer and the article describing the research was published last month in the specialized journal Nejm (The New England Journal of Medicine).

In order to assess the effects of vaccinating pregnant women on the protection of babies, data on admission and hospitalization of 3,570 babies born to mothers who received the vaccine were recorded, while 3,558 were born to pregnant women who received a placebo. The study period was from June 17, 2020 to October 2, 2022.

In the analyzed period, the incidence of cases of respiratory disease in the placebo group was about twice that observed in the research arm that received the immunizer. There were 56 (1.6%) cases of respiratory infection in babies in the control group, against 24 (0.7%) in babies passively immunized up to 90 days after birth.

In the first two months of age, the incidence of bronchiolitis cases in the placebo group was almost 1.5 times greater than that observed in immunized individuals (81 versus 35, or 2.3% versus 1%) and, finally, after 180 days (6 months old), the proportion of cases in the control group doubled in the control group compared to the vaccinated group (117 or 3.4% versus 57 or 1.6%).

One of the limitations of the study is that it was conducted during the Covid-19 pandemic, when the frequency and circulation of other respiratory viruses, such as influenza, adenovirus and RSV itself, were altered.

According to the survey, about a fifth of all hospitalizations for respiratory illnesses in infants up to six months old were for bronchiolitis caused by RSV. The rate observed in the pre-pandemic period was 50% to 80% of all hospitalizations for bronchiolitis having RSV as the etiological agent, and about 40% of cases of pneumonia in children under one year old.

The vaccine is formulated with a virus glycoprotein in a pre-fusion format, that is, before being “presented” by the body’s cells for recognition by our immune system. It combines the protein of two subtypes of the virus, the most common in circulation.

In addition to the test vaccine, therapies with monoclonal antibodies already exist to prevent the hospitalization of babies up to two years old for bronchiolitis. In these cases, as the baby’s immune system is still immature and cannot provide its own protection, the antibodies are already injected directly, but they usually have a protection of a maximum of two years.

Pregnant vaccination research can help produce a low-cost, widely accessible form of immunization for low- and middle-income countries by routinely vaccinating mothers against RSV during antenatal care, thereby reducing cases of infection. in the first six months of life, a critical period for babies.