Vanderbilt was the lead site for an NIH-funded, phase 2, multicenter influenza vaccine study in pediatric allogeneic hematopoietic stem cell transplant (HCT) recipients that may lead to a change in the current flu vaccine recommendations in this vulnerable population.
The study was published in the New England Journal of Medicine, and the authors found that two doses of high-dose trivalent flu vaccine resulted in higher amounts of influenza-specific antibodies than two doses of standard dose quadrivalent vaccine.
“Historically, recommendations for flu vaccination for HCT recipients have been based on prior flu studies with small sample sizes or based on expert opinion,” said Natasha Halasa, MD, MPH, professor of Pediatric Infectious Diseases at Monroe Carell Jr. Children’s Hospital at Vanderbilt. “We know pediatric HCT recipients do not respond as well to the flu vaccine compared to healthy children, especially in the early post-HCT period. They are one of the most immunocompromised populations. Further, since flu is associated with high morbidity and mortality in this high-risk group, determining the optimal vaccine strategy is important.
Halasa and her team conducted three prior phase 1 studies comparing one dose of high-dose flu vaccine to one dose of standard dose and proved that high-dose flu vaccine was safe in three populations (children with acute lymphoblastic leukemia, pediatric solid organ transplant recipients, and adult HCT recipients), but data were lacking for pediatric HCT recipients.
Participants included in this recent study were between 3-17 years old and had received an allogeneic HCT during the past three to 35 months.
Carrie Kitko, MD, associate professor of Pediatrics and director of the Pediatric HCT Program at Monroe Carell, said the study’s findings are critical as stem cell providers learn how best to vaccinate their patients post-HCT.
“The last thing we want to do is provide a vaccine that gives a patient and their family a false sense of security that they have protection from a particular infection,” said Kitko, Ingram Professor of Pediatric Oncology.
“The more we know about timing of vaccinations post-HCT and how many doses result in the best immune response, the better.”
The $4.8 million, three-year grant included nine sites in the United States. A total of 170 participants were enrolled, and each participant received either two vaccine doses of the high-dose trivalent influenza vaccine or two doses of the standard dose quadrivalent influenza vaccine during flu seasons between 2016-2019. The two doses were given 28 to 42 days apart.
According to study findings, two doses of the high-dose trivalent vaccine resulted in higher antibody responses compared to the standard dose regimen.
“We are hoping that these results will help health care providers and policymakers make informed decisions about how best to vaccinate this group of patients,” said Halasa.
Kitko expects the results to impact the vaccination practice used by pediatric stem cell transplant providers.
“I know here at Monroe Carell we hope to follow these new guidelines during the next flu season this fall.”
