Study suggests birth dose of pertussis vaccine could be safe, effective

Nicholas Wood, MB, BS, PhD

Maternal pertussis vaccinations have been recommended in the United States for the last 5 years, but a new Australian study shows that vaccination at birth also may be an option.

Pertussis is a severe respiratory infection that is particularly dangerous for infants. The number of cases is rising, and infants may not be vaccinated themselves until age 2 months, according to US vaccination schedules. This is why the Centers for Disease Control and Prevention (CDC) began recommending maternal vaccination in 2013. Maternal vaccination allows mothers vaccinated for pertussis in late pregnancy to pass antibodies along to their infants, offering them protection until they can be vaccinated themselves. Recent research has attributed a 75% reduction in pediatric pertussis hospitalizations to maternal vaccination.

Still, the recommendation isn’t possible in all cases. Whether it’s because a mother goes without prenatal care or has a condition that prevents her from being vaccinated, some infants are still born without protection from pertussis.

For these cases, Nicholas Wood, MB, BS, PhD, of the National Centre for Immunisation Research and Surveillance (NCIRS) of Vaccine Preventable Diseases in Westmead, New South Wales, Australia, and colleagues decided to test the efficacy of pertussis vaccinations at birth in a new study published in JAMA Pediatrics. The research team found that infants vaccinated with a pertussis-only vaccine-not including diphtheria or tetanus vaccines-had an equal or better antibody response than infants who did not receive the birth dose.¹

“When mom does not get the vaccine, this is a potential option,” Wood says.

Study data supports aP birth dose

The study was conducted at 4 sites across Australia on 440 full-term infants. They were classified by maternal vaccination status-maternal receipt of tetanus toxoid, reduced diphtheria toxoid, and pertussis antigen content (Tdap) vaccine prior to pregnancy-and infants were randomly selected to receive either the acellular pertussis (aP) vaccine within 120 days of birth alongside the hepatitis B vaccine, or the hepatitis B vaccine alone.

The research team concluded that their study shows a narrowed immunity gap between birth and the receipt of a child’s first direct pertussis vaccine-a critical period during which infants are susceptible to dangerous pertussis infection.

The study found that more infants given a single dose of the aP vaccine at birth alongside their hepatitis B vaccine had detectable antibodies by 10 weeks of age to pertussis toxin and pertactin, regardless of whether or not their mothers had received Tdap vaccinations in the previous 5 years. The research team also found that the infants’ immunoglobulin-G antibody responses to pertussis toxin were 4 times higher in the infants vaccinated with the birth dose of the pertussis vaccine than their peers. The infants vaccinated at birth also had higher levels of pertussis antibodies than the control group at 6 weeks of age, regardless of the maternal vaccination.

Birth doses of the vaccine were generally well tolerated, but some fevers were reported. However, the study notes that fever rates were similar among those infants vaccinated with the pertussis vaccine at birth and those who were not.

Although the aim of the study was not to usurp current recommendations for maternal vaccination, the study does reference recent research suggesting that maternal antibodies present at birth can possibly reduce an infant’s own antibody responses to pertussis, diphtheria, and diphtheria-related vaccines.

“Our study findings are consistent with others showing that detectable maternal antibody at birth is associated with lower pertussis antibody responses after the primary immunization schedule,” the report states. “In our study, this result was seen in both the infants who received the aP vaccine and those in the control group. The clinical significance of reductions in pertussis antibody related to maternal interference will require ongoing clinical evaluation because there are no accepted serologic correlates of protection.”

Another consideration of the study is the availability of a pertussis-only vaccine. Wood says most companies produce a combination vaccine, and a pertussis-only vaccine was developed specifically for this study. No pertussis-only vaccines are commercially available at this time, so one would have to be developed in order for the birth dose to be given in the clinical setting on a more widespread basis. Additionally, the research team did not investigate the efficacy of the birth dose of pertussis in premature infants.

Wood says the study doesn’t seek to undermine the maternal vaccination recommendation, but says the results indicate that birth doses of pertussis-only vaccine could be an option for protection when, for whatever reason, mothers were not able to be vaccinated themselves.

"The bottom line is that when mom did not get vaccine during pregnancy, then the baby that is born to that mom could get a birth dose,” Wood says.

References:

1. Wood N, Nolan T, Markshall H. Immunogenicity and safety of monovalent acellular pertussis vaccine at birth: a randomized clinical trial. JAMA Pediatrics. September 10, 2018. Epub ahead of print.