Prevalence and correlates of diphtheria toxoid antibodies in children and adults in Israel

The Israel National Sera Bank: Methods, Representativeness, and Challenges

The Israel National Sera Bank (INSB) was established in 1997 in the Israel Center for Disease Control. The purpose of the INSB was to provide policymakers with data on the immunity status of the Israeli population against vaccine-preventable diseases, and on the extent and characteristics of exposure to emerging and re-emerging infectious diseases. The aim of this paper is to describe the methods, representativeness, and challenges in maintaining the INSB. The INSB comprises residual sera collected in six laboratories. By the end of 2019, 138,898 samples had been deposited in the INSB. These include samples from four community laboratories: 30.7% from the National Blood Service, 22.2% from Haifa and the Western Galilee, 21.7% from Soroka, and 0.7% from Jerusalem; and from two medical center laboratories: 18.6% from Schneider and 6.1% from Mayanei Hayeshua. The demographic characteristics of the sample at the end of 2019 closely resembled those of the general population. The main challenges addressed in maintaining the INSB relate to its representativeness, the possibility of repeated donors, costs, stability of antibody levels after long-term storage, ethical aspects, and the data available for each sample. The INSB is a unique, powerful, and necessary tool for assessing population immunity levels, based on serum samples collected over a long period of time.

Use of tetanus-diphtheria (Td) vaccine in children 4-7 years of age: World Health Organization consultation of experts

For lifetime protection against diphtheria and tetanus, the World Health Organization (WHO) recommends six doses of diphtheria and tetanus containing vaccines. Td (reduced diphtheria toxoid, ≥2-5 IU) vaccines are currently licensed for ages 7 years and older, but use of Td vaccine for ages 4 years and older would have advantages for immunization programs in many low- and middle-income countries. For this reason, WHO convened an expert consultation to review the currently available evidence for the use of Td vaccine from 4 to 7 years of age which concluded: (1) no relevant biological difference in immune response in the relevant age group compared with children over 7 years of age; (2) adequate seroprotection in several studies with Td vaccine in the 4-7 age group and many studies using combination vaccines; (3) durable and protective response of at least 9-11 years duration in several longitudinal and modelling studies, (4) less reactogenicity compared with use of full-dose diphtheria vaccine, potentially improving the vaccination experience; and (5) adequate control of diphtheria in several countries using Td-containing combination vaccines in 4-7 year old children. On this basis, the experts concluded that from a programmatic perspective, Td vaccine given in ages 4-7 years, as a second booster dose in a six-dose series, would provide adequate protection against diphtheria and tetanus and recommended steps to include this change in age extension listed in the package insert.

Antitoxins for diphtheria and tetanus decline more slowly after vaccination with DTwP than with DTaP: a study in a Chinese population

OBJECTIVES

DTP vaccines are used for the prevention of pertussis, diphtheria and tetanus. In 2007, in Gaobeidian city, China, the DTwP vaccine was replaced with DTaP. This study described the diphtheria and tetanus sero-epidemiology in subjects vaccinated solely with DTwP or DTaP.

METHODS

Blood samples were obtained between October 2012 and June 2013 from 587 healthy subjects aged 2-17 years. Serum IgG antibodies against diphtheria and tetanus were determined using ELISA. Interrupted time series analyses examined the changes in antitoxin levels over time and analyzed the alterations in diphtheria and tetanus antitoxin levels after the vaccine switch.

RESULTS

Mean concentrations of diphtheria antitoxin and tetanus antitoxin were 0.074 IU/ml (95% CI 0.065-0.084) and 0.063 IU/ml (95% CI 0.053-0.076). The protection rates (antitoxins >0.01 IU/ml) for diphtheria and tetanus were 88.25% and 82.11%. Mean antitoxin levels for both diphtheria and tetanus decreased with increasing age, but this decrease was much slower for DTwP than DTaP.

CONCLUSIONS

Although the observed protection rates for diphtheria and tetanus were sufficient to prevent an outbreak at present, the means levels of diphtheria and tetanus antitoxins decreased with increasing age; therefore, booster vaccinations at 7 and 12 years of age would be strengthened in Gaobeidian city, China.