Humoral responses to independent vaccinations are correlated in healthy boosted adults

Investigation of the baseline tetanus antibody level and its persistence in a military unit

OBJECTIVES

To determine tetanus antibody levels in army recruits and evaluate the persistence of immunity following tetanus booster immunization in adults.

METHODS

A total of 680 recruits were selected for observation of their tetanus antibody levels. From 2005 to 2015, 691 peacekeepers with tetanus vaccination were included in the questionnaire-based and serological survey based on cluster stratification. The tetanus antibody-positive rate, geometric mean concentration (GMC), and their respective changes over time were analyzed in different age groups, regions, and years after tetanus booster immunization.

RESULTS

The positivity rates of tetanus antibodies in the recruits and peacekeepers were 74.85% and 99.86%, respectively (χ² = 193.00, P < 0.05) and the antibody GMCs were 0.05 and 0.70 IU/mL (t = 15.73, P < 0.05). The antibody positivity rates of recruits from 12 provinces ranged from 47.62% (Hubei) to 100% (Inner Mongolia) (χ² = 37.24, P < 0.05) and the antibody GMCs ranged from 0.02 (Hubei) to 0.09 IU/mL (Heilongjiang) (F = 5.19, P < 0.01). Among the 691 peacekeepers, no statistically significant difference in antibody positivity rate was detected between men and women. After administration of one booster dose of the tetanus vaccine, a protective antibody level was calculated to persist up to 22 years; a significant difference in antibody levels was observed within 10 years between one and two or more booster doses.

CONCLUSION

The rate at which recruits tested positive for tetanus antibodies was low. Thus, it is necessary to screen for tetanus antibodies during military recruitment and implement a precision-based booster immunization protocol for tetanus vaccine. Moreover, one dose of the tetanus vaccine booster has been calculated to maintain a protective antibody level up to 22 years, without the need for repeated reinforcements during this period.

Incidence of Tetanus and Diphtheria in Relation to Adult Vaccination Schedules

BACKGROUND

The World Health Organization (WHO) does not recommend routine adult booster vaccination for tetanus and diphtheria after completion of the childhood vaccination series. However, many countries continue to implement adult booster vaccinations, leading to the question of whether this is necessary to reduce the incidence of these 2 rare diseases.

METHODS

We conducted an observational cohort study based on WHO case reports from 2001 through 2016. We compared the incidence of tetanus and diphtheria in 31 North American and European countries that either do or do not recommend adult booster vaccination.

RESULTS

Countries that vaccinate adults every 5-20 years (group 1) were compared with countries that do not routinely vaccinate adults for tetanus or diphtheria (group 2). Comparison of group 1 vs group 2 revealed no significant decline in tetanus incidence rates among countries that vaccinate adults (P = .52; risk ratio [RR] = 0.78; 95% confidence interval [CI], .36 to 1.70). The risk of contracting diphtheria was increased among countries that vaccinate adults due to inclusion of Latvia, a country that had poor vaccination coverage (P < .001). However, if Latvia is excluded, there is no difference in diphtheria incidence between countries that do or do not routinely vaccinate adults (P = .26; RR = 2.46; 95% CI, .54 to 11.23).

CONCLUSIONS

Review of >11 billion person-years of incidence data revealed no benefit associated with performing adult booster vaccinations against tetanus or diphtheria. Similar to other vaccines, this analysis supports the WHO position on adult booster vaccination and, if approved by governing health authorities, this may allow more countries to focus healthcare resources on vulnerable and undervaccinated populations.

Anti-polysaccharide and anti-diphtheria protective antibodies after 13-valent pneumococcal conjugate vaccination in rheumatoid arthritis patients under immunosuppressive therapy

Immunogenicity of 13-valent pneumococcal polysaccharide (PnPS) conjugate vaccine (PCV13) was evaluated in 38 rheumatoid arthritis patients under immunosuppressive treatment and 20 healthy controls (HC). Antibodies to all PnPS and diphtheria-toxin analogue conjugate protein were measured pre- (T0), 1 (T1), 6 (T2), 12 (T3) months post-immunization. Patients and HC had similar response to individual PnPS. Mean antibody levels to all PnPS but one doubled at T1 compared with T0, with T3 persistence for only 8-7/13 PnPS. Baseline antibody levels was inversely associated with the rate of responders at T1 (T1/T0≥2) to 11/13 PnPS. Few subjects reached protective IgG levels against some serotypes frequently isolated in Italian patients with invasive pneumococcal disease. Antibody response was not influenced by therapy, except the one to PS7F, which was reduced by tumor necrosis factor-α-inhibitors. Vaccination increased also anti-diphtheria IgG. Despite this study substantially confirmed the PCV13 immunogenicity in immunocompromised patients, it also revealed some limitations.

Lifelong Maintenance of Oral Tolerance and Immunity Profiles in Mice Depends on Early Exposure to Antigen

Oral tolerance is defined as a state of systemic hyporesponsiveness to an antigen that has been previously administered by the oral route. Many factors affect oral tolerance induction; some of them related to antigen, and some related to the animal. The age of the animal is one of the most important factors that affect oral tolerance as ageing brings many alterations in immune responses. Herein, we demonstrated that both the oral tolerance and pattern of immune reactivity triggered in early life were kept up to 15 months regarding the magnitude of antibody production, cell proliferation and cytokine profile when compared to immune responses induced in old mice. Therefore, our results corroborate with a promising proposal for prevaccination during childhood and young age, and a booster in older age, to make sure that the primary immunization in early life is not lost in aged individuals.

Anthrax Vaccine Precipitated Induces Edema Toxin-Neutralizing, Edema Factor-Specific Antibodies in Human Recipients

Edema toxin (ET), composed of edema factor (EF) and protective antigen (PA), is a virulence factor of Bacillus anthracis that alters host immune cell function and contributes to anthrax disease. Anthrax vaccine precipitated (AVP) contains low but detectable levels of EF and can elicit EF-specific antibodies in human recipients of AVP. Active and passive vaccination of mice with EF can contribute to protection from challenge with Bacillus anthracis spores or ET. This study compared humoral responses to ET in recipients of AVP (n = 33) versus anthrax vaccine adsorbed (AVA; n = 66), matched for number of vaccinations and time postvaccination, and further determined whether EF antibodies elicited by AVP contribute to ET neutralization. AVP induced higher incidence (77.8%) and titer (229.8 ± 58.6) of EF antibodies than AVA (4.2% and 7.8 ± 8.3, respectively), reflecting the reported low but detectable presence of EF in AVP. In contrast, PA IgG levels and ET neutralization measured using a luciferase-based cyclic AMP reporter assay were robust and did not differ between the two vaccine groups. Multiple regression analysis failed to detect an independent contribution of EF antibodies to ET neutralization in AVP recipients; however, EF antibodies purified from AVP sera neutralized ET. Serum samples from at least half of EF IgG-positive AVP recipients bound to nine decapeptides located in EF domains II and III. Although PA antibodies are primarily responsible for ET neutralization in recipients of AVP, increased amounts of an EF component should be investigated for the capacity to enhance next-generation, PA-based vaccines.

Lethal factor antibodies contribute to lethal toxin neutralization in recipients of anthrax vaccine precipitated

A major difference between two currently licensed anthrax vaccines is presence (United Kingdom Anthrax Vaccine Precipitated, AVP) or absence (United States Anthrax Vaccine Adsorbed, AVA) of quantifiable amounts of the Lethal Toxin (LT) component Lethal Factor (LF). The primary immunogen in both vaccine formulations is Protective Antigen (PA), and LT-neutralizing antibodies directed to PA are an accepted correlate of vaccine efficacy; however, vaccination studies in animal models have demonstrated that LF antibodies can be protective. In this report we compared humoral immune responses in cohorts of AVP (n=39) and AVA recipients (n=78) matched 1:2 for number of vaccinations and time post-vaccination, and evaluated whether the LF response contributes to LT neutralization in human recipients of AVP. PA response rates (≥95%) and PA IgG concentrations were similar in both groups; however, AVP recipients exhibited higher LT neutralization ED₅₀ values (AVP: 1464.0±214.7, AVA: 544.9±83.2, p<0.0001) and had higher rates of LF IgG positivity (95%) compared to matched AVA vaccinees (1%). Multiple regression analysis revealed that LF IgG makes an independent and additive contribution to the LT neutralization response in the AVP group. Affinity purified LF antibodies from two independent AVP recipients neutralized LT and bound to LF Domain 1, confirming contribution of LF antibodies to LT neutralization. This study documents the benefit of including an LF component to PA-based anthrax vaccines.

Immune status of representative infectious diseases among Japanese female university students

OBJECTIVE

To elucidate the immune status of representative infectious diseases among Japanese youth, we retrospectively investigated serum antibody levels in university students, partly comparing these to immunization records and infectious disease histories confirmed by the maternal and child health (MCH) handbooks.

MATERIALS AND METHODS

In total, 168 Japanese female university students, aged 20-21 years, were included. Data were collected from examinations of antibody titers against measles, rubella, varicella-zoster (VZ), mumps, and hepatitis B (HB) and C (HC) viruses, and from QuantiFERON®-TB Gold tests, between 2011 and 2015. Records of immunization and infectious disease histories were available from MCH handbooks for students who agreed with the use of their data for this study (n=23).

RESULTS

All students had positive antibodies, detected by enzyme immunoassay (EIA), against measles, rubella, VZ, and mumps; however, seroprevalences within the range of seroprotective antibody levels were 38.1% (64/168), 67.9% (114/168), 95.9% (141/147), and 89.8% (132/147), respectively. The students had probably not been infected with HB, HC, or tuberculosis at the time of the examinations.

DISCUSSION

The study indicated that a two-dose vaccine for measles and rubella (MR) might not be sufficient to produce antibodies at seroprotective levels. Therefore, we propose that health care workers, including students, should receive an additional MR vaccine, even if they have received two doses of MR vaccine or if they have unknown histories of immunizations or infectious diseases. Further investigations in these areas will be needed.

Durability of Vaccine-Induced Immunity Against Tetanus and Diphtheria Toxins: A Cross-sectional Analysis

BACKGROUND

Many adult immunization schedules recommend that tetanus and diphtheria vaccination be performed every 10 years. In light of current epidemiological trends of disease incidence and rates of vaccine-associated adverse events, the 10-year revaccination schedule has come into question.

METHODS

We performed cross-sectional analysis of serum antibody titers in 546 adult subjects stratified by age or sex. All serological results were converted to international units after calibration with international serum standards.

RESULTS

Approximately 97% of the population was seropositive to tetanus and diphtheria as defined by a protective serum antibody titer of ≥0.01 IU/mL. Mean antibody titers were 3.6 and 0.35 IU/mL against tetanus and diphtheria, respectively. Antibody responses to tetanus declined with an estimated half-life of 14 years (95% confidence interval, 11-17 years), whereas antibody responses to diphtheria were more long-lived and declined with an estimated half-life of 27 years (18-51 years). Mathematical models combining antibody magnitude and duration predict that 95% of the population will remain protected against tetanus and diphtheria for ≥30 years without requiring further booster vaccination.

CONCLUSIONS

These studies demonstrate that durable levels of protective antitoxin immunity exist in the majority of vaccinated individuals. Together, this suggests that it may no longer be necessary to administer booster vaccinations every 10 years and that the current adult vaccination schedule for tetanus and diphtheria should be revisited.