Abstract
BackgroundOwing to a declining birth rate and longer lifespan, the number of elderly people (≥ 60 years) in Thailand has grown rapidly. However, the elderly are at significant risk of infectious diseases because they have never been immunized, because they have not been completely immunized, or because their immunity has waned. Immunity against infectious diseases in the elderly is an important means of controlling diseases in the community. Our objective was to evaluate the seroprotective rate against diphtheria, tetanus, and pertussis in the elderly Thai population.MethodsIn total, 430 healthy individuals from the northeastern region of Thailand were enrolled in this study and stratified into five age groups: 60–65, 66–70, 71–75, 76–80, and > 80 years. Serum samples were collected and quantitatively analyzed for diphtheria, tetanus, and pertussis IgG antibody by using commercial ELISA kits. For anti-diphtheria toxoid and anti-tetanus toxoid ELISA, values < 0.01 IU/ml were interpreted as seronegative, and for anti-Bordetella pertussis toxin ELISA, values < 5 IU/ml were interpreted as seronegative; these definitions were in accord with previous studies.ResultsFor diphtheria toxoid Ab, the majority of the population had antibody levels > 0.01 IU/ml. For tetanus anti-toxoid Ab, the majority of the population had antibody levels of > 0.01 IU/ml, of which approximately 34% had durable antibody protection levels (DAPL) of ≥ 1 IU/ml. Meanwhile, nearly 45% of the population had an Ab level against pertussis lower than the protectivity level.ConclusionsIn total, 97.2%, 83.5%, and 55.8% of the population had a higher antibody level than the minimal protective level for diphtheria, tetanus, and pertussis, respectively. In order to prevent an outbreak of these diseases in the future, the elderly should be administered with Tdap revaccination to provide diphtheria herd immunity in the population; this will increase cocoon phenomenon for pertussis and protect the population from tetanus-prone injury.
Highlights
Owing to a declining birth rate and longer lifespan, the number of elderly people (≥ 60 years) in Thailand has grown rapidly
According to an aging society in Thailand in the near future, the present study aimed to evaluate the seroprotective rate against these three diseases in the elderly Thai population for use as criteria for the administration of vaccine boosters in the future
The data were classified according to the levels of antitoxoid: < 0.01 international units per milliliter (IU/ml), 0.01 to 0.09 IU/ ml, 0.1 to 0.99 IU/ml and ≥ 1 IU/ml, as indicated in a previous study [20]
Summary
Owing to a declining birth rate and longer lifespan, the number of elderly people (≥ 60 years) in Thailand has grown rapidly. Immunity against infectious diseases in the elderly is an important means of controlling diseases in the community. The number of elderly people (defined as ≥ 60 years) in Thailand has grown rapidly and will continue to do so in future decades. Since 1960, the number of older people in the Thai population has increased sevenfold from approximately 1.7 million (4.9%) in 1970 to 11.2 million (17.1%) by 2017 and is expected to rise to 15.6 million (or 23.4% of the total population) by 2026. Establishing immunity against all infectious diseases in this particular population is very important in the control of disease outbreaks in the future
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