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Vaccinating Correctly Is Harder Than It Looks!

January 15, 2025

In an article being early released in Pediatrics, Alexandria Albers and colleagues from the University of Montana and the University of Colorado evaluated invalid vaccine dose administration rates for 10 vaccines, including 4 not previously studied (hepatitis A, pneumococcal vaccine, rotavirus vaccine, and influenza) (10.1542/peds.2024-068341). Vaccines provided outside of recommended ages or intervals are considered invalid.

Since invalid vaccination is not routinely tracked by national surveillance (who knew?), the authors used a nationally representative database, the National Immunization Survey-Child (NIS-Child), 2011–2020, to assess vaccination timing and dose validity for children 0–35 months. In NIS-Child, parents are called by phone for vaccine history, and then a confirmatory survey is mailed to their health provider; hence the data are as accurate as possible.

This fascinating article challenges us to do better with vaccine administration! The authors found that of 161,187 children, 22,209 (weighted percent: 15.4%, 95% CI:15.0-15.8%) had an invalid vaccine dose. Of those with a minimum age or minimum interval invalid dose, fewer than half (44.9% [95% CI: 43.2-46.6%]) received the extra doses needed to complete the series as recommended by the US Advisory Committee on Immunization Practices (ACIP). In case you are wondering, since ACIP permits a 4 day “grace period” (for example, if the minimum interval between doses is 28 days, a dose at 24 days would be considered valid), doses within the 4 days window were considered valid for this study.

An informative video abstract provides the authors’ summary, and a thought-provoking commentary (10.1542/peds.2024-068972) by Dr. David G Bundy from the Medical University of South Carolina proposes 3 main categories of causality to tackle:

  1. Process—for example, a unique feature of the rotavirus vaccine, the most commonly invalid vaccine, is the series’ maximum age limit, which gives fewer opportunities to recover from delays.
  2. Product—combination vaccines can simplify vaccine administration but “combinations of combinations,” especially those including Haemophilus influenzae type B (HIB), can add adherence complexity.
  3. Patient—children with >3 providers or who had moved from state to state had a higher risk of invalid vaccine receipt, which is not surprising given the (highly unfortunate) absence of a national vaccine registry.

There is lots more to learn from this excellent study and the associated commentary. My take-home is to reflect on the importance of (1) always pursuing prior vaccine records (despite the time required and inconvenience) and (2) continually re-educating ourselves about vaccine timing. I love the Centers for Disease Control and Prevention (CDC) vaccine-specific catch-up job aids: just google “catch up guidance job aid CDC [and the vaccine name]” for a terrific resource organized by vaccine, child age, and number and timing of previous doses with the required next dose timing. My personal favorites are for Prevnar and DTaP.

Albers and colleagues did find that the rate of invalid doses decreased over time (Figure 1, prevalence decreased from 16.9% (95% CI:15.8-17.9%) in 2011 to 12.5% (95% CI: 11.5-13.4%) in 2020). Hopefully this encouraging trend will continue!

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