JMIR Publications

ABSTRACT

Background:

Post-vaccination fever (PVF) is a mild, adverse event that naturally improves without complications, but is highly prevalent and, in some cases, accompanied by febrile convulsions. These adverse effects may cause parents to delay or avoid vaccinating their children.

Objective:

This study aimed to identify PVF patterns and the ability of antipyretics to affect changes in these patterns.

Methods:

Data provided by parents of feverish children derived from a mobile application, namely, Fever Coach, was used to identify PVF patterns according to the vaccinations and the use of antipyretic drugs. We selected single vaccination records that contained five or more body temperature readings performed within 48 hours of vaccination, and we analyzed PVF onset, offset, duration, and maximum body temperature. Through observing PVF response to vaccination, we identified the effects of antipyretic drugs on PVF onset, offset, and duration times; the extent of fever; and the rate of decline. We also performed logistic regression analysis to determine demographic variables (age, weight, and sex) involved in relatively high fevers (body temperature ≥39℃).

Results:

The total number of Fever Coach users was 25037, with 3834 users having entered single vaccination records, including 4448 vaccinations and 55783 body temperature records. Most records were obtained from children receiving the following vaccinations: pneumococcus (n=2069), Japanese encephalitis (n=911), influenza (n=669), diphtheria, tetanus, and pertussis (n=403), and hepatitis A (n=252). According to the 4448 vaccination records, 3427 (77.05%) children had taken antipyretic drugs, and 3238 children took antibiotics at body temperatures >38°C (89.15%). The number of instances where this temperature threshold was reached was more than four times greater than the number where the temperature was 37.9℃. A comparative analysis of antipyretic and non-antipyretic cases showed there was no difference in onset time; however, offset and duration times were significantly shorter in non-antipyretic cases than in antipyretic cases (p<0.001). In non-antipyretic cases, offset times and duration times were, on average, 9.9 and 10.1 hours shorter, respectively, than in antipyretic cases. Body temperatures also decreased faster in non-antipyretic cases, and influenza vaccine-associated fevers lasted relatively longer, while pneumococcus vaccine-associated fevers were relatively short-lived.

Conclusions:

These findings suggest that PVF has its own fever pattern, which is dependent upon vaccine type and the presence of antipyretic drugs, and that post-vaccination temperature monitoring may ease fever phobia and reduce the unnecessary use of antipyretics in medical care.