What are common immediate side effects after a Prevnar 20 booster in adults and children?
Executive summary
Prevnar 20 most commonly causes local reactions—pain, swelling, and redness at the injection site—and short-lived systemic symptoms such as fatigue, muscle aches, headache and fever in adults, and irritability, drowsiness, decreased appetite and fever in infants and children [1] [2] [3]. These reactions are usually mild to moderate, occur within the first day or two after vaccination, and resolve within a few days; serious adverse events were not considered related to the vaccine in Phase 3 trials but rare allergic reactions can occur and require immediate care [3] [4] [5].
1. Common immediate side effects in adults: local pain, muscle aches, fatigue and headache
Clinical trial and product safety information list the most frequent post‑dose complaints in adults (≥18 years) as pain at the injection site, muscle pain, fatigue, headache and joint pain, with injection site swelling especially noted in younger adults aged 18–59 [1] [6] [3]. Manufacturer and clinical resources consistently report these events as occurring at a rate greater than 1 in 10 (very common) or greater than 1 in 100 (common), depending on the symptom and age cohort [1] [3] [7].
2. Common immediate side effects in infants and children: irritability, injection‑site reactions, drowsiness and fever
For infants and children on the routine 4‑dose schedule, the patterns differ: the most frequently observed reactions are irritability, pain, redness and swelling at the injection site, drowsiness or increased sleep, decreased appetite, and fever—again typically described as very common in pediatric trial data [1] [8] [3]. Older children and adolescents also commonly experienced fatigue, muscle pain and headache, and fever is especially common in children under 5 years [3] [8].
3. Timing, expected severity and typical duration of immediate reactions
Available regulatory and product documents indicate these side effects generally begin soon after vaccination—most within 24–48 hours—are mild to moderate in intensity, and resolve within a few days without specific treatment beyond symptomatic measures (cold compresses, analgesics where appropriate) [3] [9] [1]. Clinical trials and post‑marketing summaries describe the majority of local and systemic reactions as transient and self‑limited, mirroring experience with earlier Prevnar formulations [4] [10].
4. Serious reactions, contraindications and vulnerable groups
Serious adverse events observed in trials were judged consistent with background medical conditions and not considered related to Prevnar 20, but immediate severe allergic reactions (anaphylaxis) are a recognized, rare possibility and the vaccine should not be given to anyone with a known severe allergy to vaccine components or to diphtheria toxoid used in the conjugate [4] [6] [5]. Regulatory guidance flags that adults with weakened immune systems may have a reduced immune response and that safety data are limited for certain special populations, so clinicians should weigh risks and benefits in those groups [6] [4].
5. Practical expectations: when to call a clinician and how events are tracked
Providers advise that routine local and systemic reactions do not usually require medical care, but signs of an allergic reaction—hives, difficulty breathing, swelling of face, lips, tongue or throat—warrant emergency help, and any worrying or persistent symptom should prompt contact with a health professional [5] [9]. Patients and providers are encouraged to report adverse events to public health systems (FDA/CDC reporting channels) so post‑marketing surveillance can continue to refine the safety profile [1] [11].