Measles: Complications & Vaccination

Measles (rubeola) is an acute, highly contagious viral exanthem caused by a single-stranded RNA Morbillivirus of the family Paramyxoviridae. For NEET PG it is a perennial favourite — Koplik's spots, the cephalocaudal rash sequence, the feared complication SSPE, vitamin A dosing, and the MR/MMR schedule under India's Universal Immunisation Programme (UIP) are repeatedly tested.

Definition & Basic Virology

Measles is caused by the measles virus, an enveloped, non-segmented, negative-sense ssRNA paramyxovirus. Humans are the only reservoir (no animal or environmental reservoir), which is why measles is theoretically eradicable. The virus carries two key surface glycoproteins:

• H (haemagglutinin) protein — mediates attachment to host cell receptors (SLAM/CD150 on immune cells and nectin-4 on epithelial cells).
• F (fusion) protein — causes cell-to-cell fusion producing the characteristic multinucleate giant cells (Warthin–Finkeldey cells).

There is a single serotype, which is the reason a live attenuated vaccine confers lifelong immunity.

High-yield: Measles is the most contagious of all the classic childhood exanthems, with a basic reproduction number (R₀) of 12–18. Spread is by respiratory droplets and airborne aerosols; the virus survives in the air for up to 2 hours.

Transmission & Infectivity

• Incubation period: 10–14 days (range 7–21).
• Period of infectivity: 4 days before to 4 days after the appearance of rash. Maximal communicability is during the prodromal (catarrhal) stage.
• Secondary attack rate in susceptible household contacts exceeds 90%.

Feature	Value
Causative organism	Measles virus (Paramyxoviridae, Morbillivirus)
Genome	ssRNA, negative-sense, non-segmented
R₀	12–18 (highest of exanthems)
Incubation	10–14 days
Infective period	4 days before to 4 days after rash
Mode of spread	Droplet + airborne aerosol
Reservoir	Humans only

Pathophysiology

Virus enters via the respiratory epithelium and conjunctiva → replicates locally and in regional lymph nodes → primary viraemia seeds the reticuloendothelial system → secondary viraemia disseminates to skin, respiratory tract, conjunctiva, gut, and at times the CNS. Measles causes a profound, transient immunosuppression — it depletes pre-existing memory lymphocytes (so-called "immune amnesia"), explaining the heightened susceptibility to secondary bacterial infections (pneumonia, otitis media) and reactivation of latent tuberculosis for weeks to months after recovery.

Clinical Features

The classic course runs through three stages.

Prodrome (catarrhal stage, 3–4 days) → high-grade fever with the "3 Cs": Cough, Coryza, Conjunctivitis → toward the end, Koplik's spots appear.

Koplik's spots are the pathognomonic enanthem — tiny bluish-white/grey specks on an erythematous base, classically described as "grains of salt on a red background," seen on the buccal mucosa opposite the 2nd molars. They appear 1–2 days before the rash and fade as the rash erupts.

High-yield: Koplik's spots are pathognomonic of measles and precede the skin rash. They are the single most-asked clinical sign of measles.

Exanthem (eruptive stage):

• An erythematous maculopapular (morbilliform) rash that blanches early.
• Cephalocaudal spread: begins behind the ears and at the hairline/forehead → face → trunk → extremities (including palms and soles by day 3).
• Fever typically peaks with the rash; persistence of fever beyond 3–4 days of rash signals a complication.

Convalescence: Rash fades in the order it appeared, leaving brownish staining and fine branny desquamation (not on palms/soles). The cough may be the last symptom to resolve.

Mnemonic — the 3 Cs of the measles prodrome: Cough, Coryza, Conjunctivitis (and Koplik's spots make it memorable as the "4th C").

Differential Diagnosis of Maculopapular Exanthems

Disease	Agent	Rash & distinguishing feature
Measles	Measles virus	Cephalocaudal morbilliform rash, Koplik's spots, 3 Cs, high fever with rash
Rubella	Rubella virus	Milder, faster-spreading rash; suboccipital/postauricular lymphadenopathy, Forchheimer spots
Roseola (exanthem subitum)	HHV-6/7	High fever first, rash appears as fever falls; rash on trunk
Erythema infectiosum (5th disease)	Parvovirus B19	"Slapped cheek" appearance, lacy reticular rash
Scarlet fever	Group A Streptococcus	Sandpaper rash, circumoral pallor, strawberry tongue, Pastia's lines
Drug rash	—	Temporal link to drug, pruritus, no enanthem

High-yield: Rubella's hallmark is posterior auricular and suboccipital lymphadenopathy; roseola's hallmark is rash appearing as the fever subsides. These contrasts are favourite single-best-answer distractors.

Diagnosis & Investigation of Choice

Measles is largely a clinical diagnosis. Laboratory confirmation (essential for surveillance and outbreak/elimination programmes):

• Investigation of choice / first-line confirmatory test: serum measles-specific IgM by ELISA — detectable from rash onset and for ~1 month. A single positive IgM in an acutely ill, unvaccinated patient confirms disease.
• A four-fold rise in IgG between acute and convalescent sera is also confirmatory.
• RT-PCR of throat/nasopharyngeal swab, urine, or blood detects viral RNA and allows genotyping (used to track transmission chains in the elimination programme).
• Blood picture: leucopenia with relative lymphopenia is typical.
• Cytology may show Warthin–Finkeldey multinucleate giant cells.

High-yield: The confirmatory test for an acute case is measles-specific IgM ELISA; genotyping is done by RT-PCR under the elimination strategy.

Complications

Complications are the highest-yield part of this topic. They are commonest in children under 5, adults over 20, the malnourished (especially vitamin A deficient), the immunocompromised, and pregnant women.

Respiratory

• Pneumonia — the commonest cause of death in measles. May be:
  • Secondary bacterial (Strep. pneumoniae, Staph. aureus, H. influenzae) — most common, OR
  • Primary viral giant-cell (Hecht's) pneumonia — seen in the immunocompromised, often without rash.
• Otitis media — the commonest overall complication.
• Laryngotracheobronchitis (measles croup), bronchiolitis.

Neurological

Complication	Timing	Mechanism	Outcome
Acute post-measles encephalitis	~Days after rash (≈1 in 1000)	Immune-mediated (autoimmune/demyelinating)	~15% mortality, ~25% sequelae
Acute disseminated encephalomyelitis (ADEM)	Within weeks	Post-infectious demyelination	Variable
Measles inclusion body encephalitis (MIBE)	Weeks–months	Direct viral, immunocompromised hosts	Often fatal
SSPE	7–10 years later	Persistent defective virus in CNS	Uniformly fatal

Subacute sclerosing panencephalitis (SSPE) is the classic exam complication:

• Occurs 7–10 years after natural measles (higher risk if infection occurred before 2 years of age).
• A slow, progressive neurodegenerative disorder: stage 1 behavioural/cognitive decline → stage 2 myoclonic jerks + seizures → stage 3 rigidity/decerebration → stage 4 mutism, autonomic failure, death.
• EEG: periodic complex bursts (Radermecker complexes) — high-voltage slow-wave bursts every 4–15 seconds, synchronous with myoclonus.
• CSF: raised measles antibody titres with elevated CSF:serum IgG (oligoclonal bands).
• Prognosis: invariably fatal; no curative treatment (trials of isoprinosine/inosine pranobex ± intrathecal interferon-α only slow progression).

High-yield: SSPE appears 7–10 years after measles, shows periodic EEG complexes and myoclonus, and is uniformly fatal. Measles vaccination dramatically reduces SSPE incidence and the vaccine itself does NOT cause SSPE.

Other

• Gastrointestinal: diarrhoea (a major cause of death in developing countries), stomatitis, appendicitis.
• Eye: keratoconjunctivitis and corneal ulceration — a leading cause of childhood blindness in vitamin A–deficient children.
• Reactivation/worsening of tuberculosis (transient cutaneous anergy; a measles attack can convert a positive tuberculin test to negative).
• Subacute measles in immunocompromised — frequently fatal, may occur without rash.
• In pregnancy: increased risk of miscarriage, prematurity, low birth weight (measles is not classically teratogenic — that is rubella).

High-yield: Otitis media = commonest complication; pneumonia = commonest cause of death; SSPE = most feared/dreaded late complication. This triad of "commonest/commonest-fatal/most-feared" is a classic MCQ stem.

Management

There is no specific antiviral therapy; treatment is supportive plus targeted measures.

Supportive care → antipyretics (paracetamol), hydration and oral rehydration for diarrhoea, nutrition, eye and mouth care, and antibiotics only for proven secondary bacterial infection (no role for prophylactic antibiotics).

Vitamin A — the high-yield therapeutic

WHO recommends vitamin A for ALL children with acute measles, regardless of nutritional status, because it reduces measles morbidity, mortality, and ocular complications (xerophthalmia, blindness).

Age	Vitamin A dose (orally), once daily × 2 days
< 6 months	50,000 IU
6–11 months	1,00,000 IU
≥ 12 months	2,00,000 IU

A third dose is given 2–4 weeks later if there are clinical signs of vitamin A deficiency (e.g., Bitot's spots, xerophthalmia).

High-yield: Two daily doses of vitamin A are given to every child with measles; the dose is age-based (50,000 / 1,00,000 / 2,00,000 IU), with a 3rd dose at 2–4 weeks if ocular signs of deficiency are present.

Ribavirin has been used in severe measles or immunocompromised patients (e.g., giant-cell pneumonia) but is not routine.

Prevention & Vaccination

The vaccine

The measles vaccine is a live attenuated vaccine (Edmonston-derived strains, e.g., Edmonston-Zagreb/Schwarz in India). It is given combined as MR (measles–rubella) under UIP, or as MMR in the private sector.

• Storage: maintained at 2–8 °C; sensitive to heat and light; reconstitute with the diluent supplied and discard within 4 hours.
• Route/dose: 0.5 mL subcutaneous (deltoid/anterolateral thigh).
• Efficacy: ~85% seroconversion at 9 months, ~95% at ≥12 months; two doses give ~99% protection.
• Contraindications: pregnancy, severe immunodeficiency (e.g., advanced AIDS), anaphylaxis to a prior dose/component. Note: HIV-infected children who are not severely immunosuppressed SHOULD be vaccinated because wild measles is dangerous in them. Egg allergy is not a contraindication to MMR.
• Adverse effects: mild fever and transient rash 5–12 days post-vaccination; rare febrile seizures; transient thrombocytopenia (with MMR). The vaccine does not cause autism and does not cause SSPE.

Schedule under India's UIP

Dose	Age	Vaccine
MR-1	9–12 months (completed 9 months)	Measles–Rubella
MR-2	16–24 months	Measles–Rubella

Why 9 months in India? Maternal antibodies wane by ~9 months and measles circulation/mortality is high in infancy — so the first dose is given earlier than in the West (where 12–15 months is typical). In an outbreak or for travel, a dose may be given as early as 6 months, but that dose is not counted and the routine two doses must still be given.

High-yield: Under UIP, the schedule is MR at 9 months and again at 16–24 months (given with DPT booster). A dose before 9 months (down to 6 months) does not count toward the two-dose schedule.

Post-exposure prophylaxis (PEP)

The choice depends on the contact's immune status and timing.

Step-wise approach to a susceptible exposed contact:

1. Live MR/MMR vaccine within 72 hours of exposure → preferred for immunocompetent susceptible contacts ≥6 months (provides protection and counts as a dose if ≥9 months).
2. Human normal immunoglobulin (IG) within 6 days of exposure → for those in whom vaccine is contraindicated or who are high-risk:
   • Infants < 6 months / < 12 months depending on guideline,
   • Pregnant women (non-immune),
   • Immunocompromised individuals (regardless of prior vaccination).
3. Dose: IM immunoglobulin 0.25 mL/kg (immunocompetent) or 0.5 mL/kg (immunocompromised), max 15 mL; IVIG 400 mg/kg for those already receiving it.

High-yield: Vaccine within 72 hours OR immunoglobulin within 6 days of exposure. Immunoglobulin (not the live vaccine) is the PEP of choice in pregnant, immunocompromised, and very young infant contacts, because live vaccine is contraindicated in them. After IG, the live vaccine must be deferred (~5–6 months) before it can be given.

Measles & the Elimination Programme

India targets measles–rubella elimination. Surveillance relies on case-based investigation with IgM confirmation and genotyping by RT-PCR, plus achieving ≥95% two-dose MR coverage. A suspected case is defined (WHO) as any person with fever and maculopapular rash with cough, coryza, or conjunctivitis.

Recently asked / exam angle

• Pathognomonic sign: Koplik's spots on buccal mucosa opposite the 2nd molars, appearing before the rash — repeatedly asked.
• Rash sequence: cephalocaudal, starting behind the ears; fever peaks with rash. Distractor stems compare this with roseola (rash after fever) and rubella (lymphadenopathy).
• SSPE: image/EEG-based questions on periodic Radermecker complexes, latency of 7–10 years, myoclonus, and "uniformly fatal" outcome.
• Vitamin A dosing table by age, and the "give to all measles cases" rule — very commonly tested numerical recall.
• MR schedule (9 mo + 16–24 mo) and reason for the 9-month dose in India.
• PEP: vaccine within 72 h vs immunoglobulin within 6 days, and "immunoglobulin for the immunocompromised/pregnant contact."
• "Commonest complication (otitis media) vs commonest cause of death (pneumonia)" pairing.
• Most contagious exanthem / highest R₀ — single-line factual.

Rapid revision

1. Measles = ssRNA paramyxovirus; humans only reservoir → eradicable; single serotype.
2. Most contagious exanthem; R₀ 12–18; airborne; infective 4 days before to 4 after rash.
3. Prodrome = 3 Cs (cough, coryza, conjunctivitis) + high fever.
4. Koplik's spots = pathognomonic, buccal mucosa opposite 2nd molars, before rash.
5. Rash = morbilliform, cephalocaudal, fever peaks with rash, fades with branny desquamation + brown staining.
6. Otitis media = commonest complication; pneumonia = commonest cause of death.
7. SSPE = 7–10 yrs later, myoclonus + periodic EEG complexes, raised CSF measles antibody, fatal.
8. Confirmatory test = measles-specific IgM ELISA; RT-PCR for genotyping. Warthin–Finkeldey giant cells on cytology.
9. Vitamin A for ALL cases × 2 days: 50,000 / 1,00,000 / 2,00,000 IU by age; 3rd dose if ocular deficiency signs.
10. UIP schedule: MR at 9 mo and 16–24 mo; dose before 9 mo (down to 6 mo) doesn't count.
11. PEP: vaccine ≤ 72 h (immunocompetent) or immunoglobulin ≤ 6 days (pregnant, immunocompromised, young infant).
12. Vaccine is live attenuated, SC; contraindicated in pregnancy/severe immunosuppression; egg allergy is NOT a contraindication; does NOT cause SSPE or autism.