# P-1437. The Effect of Pre-Vaccination Analgesics on Influenza Vaccine Immunogenicity

## TL;DR

This study found that taking pain relievers before getting a flu shot does not significantly affect how well the vaccine works, though acetaminophen might help more than other types.

## Contribution

The study is the first to examine the effect of pre-vaccination analgesic use on influenza vaccine immunogenicity in a large clinical trial.

## Key findings

- Pre-vaccination analgesic use did not significantly impact the average change in antibody titers.
- Acetaminophen showed a higher, though not statistically significant, seroconversion rate compared to NSAIDs.
- There were no significant differences in immunogenicity based on the type of analgesic used.

## Abstract

Analgesics are sometimes taken prior to vaccination to prevent adverse reactions. Although several studies have examined the immunogenicity impact of post-vaccination analgesics, few have assessed the effect of analgesics taken prior to vaccination. This study compares antibody responses to hemagglutination (HA) among adults with and without analgesic use prior to influenza vaccine receipt. It further analyzes differences in immunogenicity according to analgesic type.

Pragmatic Assessment of Influenza Vaccine Effectiveness in the DoD (PAIVED) was an open-label, randomized clinical trial comparing the effectiveness of FDA-licensed influenza vaccines on adult military healthcare beneficiaries. A subset of participants provided venous blood samples collected pre-vaccination and 30 days post-vaccination. Participants included in this analysis provided venous blood samples and reported on analgesic use within 24 hours prior to vaccine receipt.

Of 1,173 PAIVED participants with pre- and post-vaccination anti-HA antibody titers, 684 (58%) answered the analgesic question. Among those, 71 (10%) reported taking an analgesic within 24 hours prior to vaccine receipt. The most prevalent analgesics were nonsteroidal anti-inflammatory drugs (NSAIDs) including ibuprofen (total NSAIDs, n=37; ibuprofen, n=19) and acetaminophen (n=28). Those who took a pre-vaccination analgesic were significantly older and more often female (Table 1). There were no significant differences in the average change in geometric mean titer (GMT) among subjects with a pre-vaccination analgesic compared to those without, including when stratified by analgesic type (Figure 1). While a higher percentage of people who took acetaminophen seroconverted (4-fold rise in antibody titer) compared to those who took ibuprofen or other NSAIDs, this finding was not statistically significant (Figure 2).

Overall, pre-vaccination analgesic use in PAIVED did not have a significant impact on influenza vaccine immunogenicity, although there was a suggestion that acetaminophen may have a more favorable effect on anti-HA seroconversion than NSAIDs for some vaccine strains. Assessment of the interplay among factors potentially influencing these findings may provide useful insight.

All Authors: No reported disclosures