Dataset Information

Association of Diphtheria-Tetanus-Acellular Pertussis Vaccine Timeliness and Number of Doses With Age-Specific Pertussis Risk in Infants and Young Children.

ABSTRACT:

Importance

In most countries, the diphtheria-tetanus-acellular pertussis (DTaP) vaccine is administered as a 3-dose infant series followed by additional booster doses in the first 5 years of life. Short-term immunity from the DTaP vaccine can depend on the number, timing, and interval between doses. Not receiving doses in a timely manner might be associated with a higher pertussis risk.

Objective

To examine the association between number and timeliness of vaccine doses and age-specific pertussis risk.

Design, setting, and participants

This population-based, retrospective cohort study used Washington State Immunization Information System data and pertussis surveillance data from Public Health Seattle and King County, Washington. Included participants were children aged 3 months to 9 years born or living in King County, Washington, between January 1, 2008, and December 31, 2017. Data were analyzed from June 30 to December 1, 2019.

Exposures

Being undervaccinated (receiving fewer than recommended doses at a given age) or delayed vaccination (not receiving doses within time frames recommended by Centers for Disease Control and Prevention).

Main outcomes and measures

Suspected, probable, and confirmed pertussis diagnosis.

Results

A total of 316 404 children (median age, 65.2 months [interquartile range, 35.3-94.1 months]; 162 025 boys [51.2%]) as of December 31, 2017, with 17.4 million person-months of follow-up were included in the analysis. A total of 19 943 children (6.3%) had no vaccines recorded in the Immunization Information System, 116 193 (36.7%) received a vaccine with a delay, and 180 268 (56.9%) were fully vaccinated with no delay. Delayed vaccination and undervaccination rates were higher for older children (17.6% delayed or undervaccinated at age 2 months for dose 1 at 3 months vs 41.6% at age 5 years for dose 5) but improved for successive birth cohorts (52.2% for 2008 birth cohort vs 32.3% for 2017 birth cohort). Undervaccination was significantly associated with higher risk of pertussis for the 3-dose primary series (adjusted relative risk [aRR], 4.8; 95% CI, 3.1-7.6), the first booster (aRR, 3.2; 95% CI, 2.3-4.5), and the second booster (aRR, 4.6; 95% CI, 2.6-8.2). However, delay in vaccination among children who received the recommended number of vaccine doses was not associated with pertussis risk.

Conclusions and relevance

The results of this cohort study suggest that undervaccination is associated with higher pertussis risk. Short delays in vaccine receipt may be less important if the age-appropriate number of doses is administered, but delaying doses is not recommended. Ensuring that children receive all doses of pertussis vaccine, even if there is some delay, is important.

SUBMITTER: Rane MS

PROVIDER: S-EPMC8356064 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Background: Optimal timing of gestational tetanus-diphtheria-acellular pertussis (Tdap) vaccination is not well-defined. No well-established specific anti-pertussis antibody level correlates with protection, suggesting the importance of antibody quality such as avidity. We aimed to determine the effect of timing of vaccination with Tdap in pregnancy on the avidity of cord anti-pertussis toxin (PT) immunoglobulin G (IgG). Methods: Prospective study of newborns in a tertiary hospital (Melbourne, Australia) born to women vaccinated with Tdap in pregnancy. Ammonium thiocyanate was used as a bond-breaking agent to measure the avidity of anti-PT IgG using concentrations between 0.25 M (to measure low avidity antibodies) and 3 M (to measure very high avidity antibodies). Anti-PT IgG levels achieved at each ammonium thiocyanate concentration in cord samples of women vaccinated during 28-32 weeks gestation (WG) vs. 33-36 WG, and women vaccinated 5-12 vs. 1-4 weeks prior to delivery were compared using t-tests. Results: Newborns of women vaccinated with Tdap during 28-32 WG (n = 43) had statistically significant higher concentrations of medium and high avidity anti-PT IgG compared with newborns of women vaccinated during 33-36 WG (n = 47), 11.6 IU/ml (95% CI, 8.8-15.2) IU/ml vs. 6.7 IU/ml (95% CI, 5.2-8.6) and 10.1 IU/ml (95% CI, 7.4-13.8) vs. 5.7 (95% CI, 3.6-8.9) IU/ml (p = 0.007 and p = 0.035), respectively. Newborns of women vaccinated 5-12 weeks before delivery (n = 64) had statistically significant higher concentrations of high and very high avidity anti-PT IgG compared with newborns of women vaccinated within 4 weeks before delivery (n = 25), 10.3 IU/mL (95% CI, 7.9-13.4) vs. 3.3 IU/mL (95% CI, 1.7-6.4), 12.6 IU/mL (95% CI, 9.4-16.9) vs. 4.3 IU/mL (95% CI, 2.2-8.5) (all p < 0.03), respectively. Conclusions: Quantification of levels of anti-PT IgG with different avidities demonstrated that pertussis vaccination 5-12 weeks before delivery was associated with higher anti-PT IgG avidity compared with vaccination within 4 weeks before delivery. Pertussis vaccination during 28-32 WG was associated with higher anti-PT IgG avidity compared with vaccination during 33-36 WG, supporting vaccination at 28-32 over 33-36 WG for optimal protection against pertussis in infancy.

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