Acellular and whole-cell pertussis vaccines in Japan. Report of a visit by US scientists

Area of Science:

• Immunology
• Vaccinology
• Public Health

Background:

• Japan introduced acellular pertussis vaccines in late 1981.
• Over 20 million doses have been administered, primarily to children aged two years and older.
• Previous whole-cell pertussis vaccines were associated with more frequent local and febrile reactions.

Purpose of the Study:

• To evaluate the safety and efficacy of acellular pertussis vaccines used in Japan.
• To compare adverse event rates between whole-cell and acellular pertussis vaccines.
• To assess the impact of acellular pertussis vaccines on pertussis incidence.

Main Methods:

• Clinical studies and post-marketing surveillance data were analyzed.
• Adverse event rates were compared between different vaccine types and age groups.
• Vaccine efficacy was estimated through five household contact studies.
• Pertussis incidence trends were monitored from 1979 onwards.

Main Results:

• Acellular pertussis vaccines demonstrated fewer mild local and febrile reactions compared to whole-cell vaccines.
• Serious adverse events with sequelae occurred at a similar low rate in both whole-cell and acellular vaccine recipients (children aged two years).
• Vaccine efficacy estimates ranged from 78% to 92% in children aged one year and older.
• A continuous decrease in reported pertussis incidence was observed since the 1979 epidemic peak.

Conclusions:

• Acellular pertussis vaccines have shown a favorable safety profile and high efficacy in Japanese children over one year of age.
• The transition to acellular vaccines in Japan has been associated with a reduction in pertussis incidence.
• Further data on the safety and efficacy in infants are needed for potential licensure in the United States.