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In a comparative trial in children (Table 1), Boostagen TdaPgen containing the same 5 μg PTgen and FHA as in Pertagen induced a higher anti-PT and similar anti-FHA immune response based on GMC ratio to a pediatric DTaPchem-IPV containing 25 μg PTchem and FHA. (See Table 1.)
Click on icon to see table/diagram/imageAntibody persistence: Immunogenicity studies demonstrated that for pertussis antibodies after an initial Tdapchem dose, there is a rapid decline during the first year with a gradual decline afterwards (US CDC, 2018).
In a randomized trial (Table 2), Pertagen induced a booster response which persisted during the first year in 90% of vaccinees. The persistence of high neutralizing antibody titers was also shown in 85% adolescents three years after a single booster dose of Pertagen as opposed to 50% vaccinees with Tdapchem after the first year. (See Table 2.)
Click on icon to see table/diagram/imageProtection against Pertussis: For pertussis, antibody contributes to protection, but there are no well-established antibody levels which correlate absolutely with protection. However, the rapid decline in antibody levels (after one Tdap dose) is consistent with the vaccine effectiveness data that indicated rapid waning of immunity and a short duration of protection conferred by Tdap containing the chemically inactivated PT (US CDC, 2018).
In a pivotal trial in adolescents (Table 1 and Table 2), pertussis antibody concentrations declined during the first year but the anti-PT antibody levels one and three years after administration of Pertagen remained significantly higher than after Tdapchem vaccine which shows that Pertagen may confer higher immunity and longer duration of protection. In a controlled trial in children (Table 1), Boostagen containing the Pertagen aPgen antigens was also compared to a DTaP-IPV containing the same aPchem antigens as a DTaP vaccine of which efficacy was documented in a trial.
Maternal vaccination is effective in protecting infants against pertussis infection through both transfer of maternal antibodies and reduced infant exposure to pertussis (ECDC, 2018). Although there is no current correlate of protection to pertussis antigens, induction of anti-PT antibody was shown to induce protection (WHO, 2017).
In a prospective observational study (Table 3), pregnant women were exposed to aPgen-only, TdaPgen or Td-only vaccines: pertussis neutralizing antibody titers at delivery were higher in Pertagen and Boostagen groups than in Td vaccinated women. Pertagen induced a higher anti-PT response than Boostagen. Vaccination with Pertagen in the 2nd trimester of pregnancy also induced higher anti-PT concentration than when given in the 3rd trimester.
Boostagen was also compared to Tdapchem in two randomized trials in women: no difference in pertussis immune response was found after one Boostagen dose between women of child-bearing age and pregnant women nor when vaccine was given in pregnant women either during the 2nd or 3rd trimester of gestation. The pooled data in pregnant and non-pregnant women shows that Boostagen induced a higher anti-PT response at Day 28 after vaccination based on the adjusted GMC ratio of Boostagen to comparator (2.6 (98.75% CI 2.0-3.5)). Boostagen was non-inferior to comparator based on the lower limit of the 98.75% CI of the adjusted GMC ratio (>0.5 different margin). It is also above 1 different margin and hence, was considered superior.
These results indicate more effective maternal immune response and antibody transfer from mother to infant after maternal vaccination with Pertagen and Boostagen than with chemically inactivated PT (PTchem) containing vaccine. (See Table 3.)
Click on icon to see table/diagram/image
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