13.3 Influenza, COVID-19 & Vaccine-Preventable Disease

Vaccine-preventable disease is how an ordinary primary-care day becomes a public-health day. Domain II is the pattern: influenza versus COVID-19 versus measles versus pertussis versus meningococcemia. Domain III is start the antiviral, do not memorize a stale isolation calendar, notify public health, and treat the household when the organism requires it. Immunization schedules and contraindications live in chapter 3; this section is the illness, the exposure, and the emergency.

Clinic opening. An unimmunized 4-year-old has fever, cough, runny nose, red eyes, white spots on the buccal mucosa, and a rash that started at the hairline and is moving down the body. If you room that child in a crowded pediatric hallway and call it roseola, you missed measles, airborne isolation, and the health department.

Influenza: treat high-risk and severe, start early, vaccinate yearly

Influenza is abrupt fever, myalgia, headache, dry cough, and ill appearance during influenza season (or a positive test). Primary-care decisions are who needs an antiviral and who needs the ED (distress, hypoxia, dehydration, infant, deteriorating chronic disease).

Neuraminidase inhibitors (oseltamivir is the outpatient workhorse) are indicated for severe, complicated, or progressive disease and for children at high risk of complications, ideally as soon as influenza is suspected — do not wait for a send-out test if the clinical picture and season fit. High-risk groups the CPNP-PC should be able to name: age younger than 5 years (highest risk younger than 2), chronic pulmonary, cardiac, neurologic, or metabolic disease, immunocompromise, pregnancy in an adolescent, and other conditions on the current CDC influenza page. Healthy children with uncomplicated influenza may be offered antivirals, especially if you can start them early (benefit is greatest when started within 48 hours of onset). Hospitalized and severe patients still receive antivirals after 48 hours. Antibiotics are not influenza therapy unless you have a bacterial superinfection.

Annual influenza vaccine for everyone 6 months and older without a contraindication is the prevention principle. Young children may need two doses in a season depending on age and prior influenza vaccine history — check the current ACIP influenza note rather than guessing 1 versus 2. Egg allergy is not a reason to withhold influenza vaccine (see 3.2).

COVID-19: core principles, current CDC — not a memorized day count

SARS-CoV-2 presentations overlap influenza and other viral URIs. Test when it will change isolation counseling, treatment eligibility, or evaluation of a high-risk child. Isolation, masking, return-to-school, and outpatient antiviral or monoclonal eligibility change. PNCB tests core principles, not last year's poster:

• Use current CDC (and AAP) guidance at the time you practice and at the time you test.
• Do not memorize a COVID isolation day count that may already be stale.
• Vaccination follows current ACIP, not a retired brand schedule.
• High-risk children may qualify for time-sensitive outpatient therapy — look up current eligibility rather than reciting a 2022 drug list.
• MIS-C (fever, shock, KD-like mucocutaneous findings, multi-organ inflammation after SARS-CoV-2) is an emergency, not an office steroid pack.

If a stem tries to trap you on "exactly how many days to isolate in 2024," the teachable answer is: follow current CDC. That is the exam-proof sentence.

Measles: airborne, reportable, time-sensitive post-exposure care

Measles is fever, cough, coryza, conjunctivitis, Koplik spots (white lesions on buccal mucosa), then a maculopapular rash that starts on the face/hairline and spreads head-to-toe while the child is still febrile and sick. It is airborne. Do not park a suspected case in the waiting room. Mask, isolate, and notify public health immediately — measles is not a "see how they look on Monday" diagnosis.

Incubation is about 10–12 days to fever and about 14 days to rash. Infectious period is commonly taught as 4 days before through 4 days after rash onset. Post-exposure management is time-bound:

Then catch up the valid two-dose MMR series when age allows. A dose given as post-exposure prophylaxis in infancy does not finish the childhood series. Unimmunized household contacts are a public-health list, not a suggestion.

Differential: roseola (rash after fever breaks, well child), fifth disease (slapped cheek, child often well), Kawasaki (nonexudative conjunctivitis but not the 3 Cs plus Koplik), drug rash. In 2026, measles is not historical trivia.

Pertussis, varicella, meningococcal disease

Pertussis (Bordetella pertussis) is catarrhal (1–2 weeks of URI — most contagious) then paroxysmal (staccato cough, inspiratory whoop, post-tussive emesis, apnea or cyanosis in infants) then convalescent. Infants may not whoop; they may just stop breathing. PCR from a nasopharyngeal specimen supports the diagnosis; do not wait to treat a young infant or a highly suggestive case. Macrolides (azithromycin is the usual pediatric course) treat the case and all household contacts regardless of immunization status — that is chemoprophylaxis, not optional. Admit young infants. Tdap with every pregnancy, optimally in the 27–36 week window, is how you protect newborns before their own DTaP series. Cocooning with adult Tdap still matters; pregnancy Tdap is the higher-yield infant-protection move.

Varicella is pruritic lesions in crops at different stages (papule, vesicle, crust) in a centripetal distribution. Vaccinated children may have milder breakthrough disease. Supportive care in healthy children; antivirals for high-risk hosts (immunocompromise, chronic skin or lung disease, older adolescents/adults, and other Red Book groups). Isolation: airborne plus contact until lesions crust. Post-exposure: varicella vaccine within 3–5 days if eligible and unprotected; VariZIG/IG for high-risk exposures per current guidance. Zoster is dermatomal; eye involvement is same-day ophthalmology.

Meningococcal disease is an emergency. Fever plus severe headache, neck pain, photophobia, petechiae/purpura, mottling, or shock is not an office CBC. Activate EMS, support ABCs, and do not delay transfer to draw a comfort panel. Droplet precautions. Chemoprophylaxis of close contacts is a public-health action after Neisseria meningitidis is suspected or confirmed. MenACWY/MenB prevention belongs in immunization counseling; here the skill is do not send purpura fulminans home with oseltamivir.

Pinworm and travel/immigrant screening conceptually

Pinworm (Enterobius vermicularis) is nocturnal perianal itch, restless sleep, and sometimes vulvar irritation. Diagnosis: tape test on the perianal skin in the morning before bathing. Treat with albendazole or pyrantel pamoate, commonly repeated in 2 weeks, and treat household members when recurrences or multiple cases are likely. Hygiene: morning bathing, trimmed nails, washed linens. Pinworm is not an SBI and not a reason for a full abdominal workup when the story is classic.

Travel and immigrant/refugee screening is a concept, not a country-by-country flash card:

• Pre-travel: current CDC Yellow Book — hepatitis A, typhoid, meningococcal vaccine for the meningitis belt, malaria prevention, and routine series catch-up. Do not invent a universal "travel pack."
• Newly arrived children: catch-up immunizations (assume not done unless documented), TB screening (IGRA or TST by age and guidelines), hepatitis B, anemia/lead as indicated, and stool or serologic parasite evaluation when the epidemiology fits. Eosinophilia is a clue, not a diagnosis.
• You screen and refer; you do not memorize every endemic map.

Clinic vignette. A 3-week postpartum household has a coughing adolescent with post-tussive emesis. The newborn has had brief apneic pauses. Treat as pertussis: macrolide for the adolescent and the household, admit the neonate, and remember that Tdap in pregnancy was the dose that should already have happened.

Clinic close. Influenza: antivirals for high-risk and severe, start early, vaccinate every season. COVID-19: current CDC, not a memorized isolation number. Measles: 3 Cs, Koplik, head-to-toe, airborne, public health, 72-hour vaccine and 6-day IG windows. Pertussis: catarrhal then paroxysmal, treat the house, Tdap every pregnancy. Varicella: crops in different stages. Purpura and shock: meningococcus, leave now. Perianal night itch: pinworm. New arrival: catch-up shots and conceptual screening, not a trivia atlas.