The Only American Maker of Two Childhood VaccinesNarrow moat

Merck & Co. (MRK) — moat facet

Merck is the only American maker of the combined childhood MMRV vaccine and of Varivax, which makes Washington both its customer and its rulebook.

Merck states that it is the only manufacturer in the United States of the combined measles, mumps, rubella and varicella vaccine, ProQuad, and of the varicella vaccine, Varivax1. That is a moat of the oldest kind: a complex biological product made in plants that took decades to build and qualify.

ProQuad, M-M-R II and Varivax sales ($M)2,13520212,24120222,36820232,48520242,4512025Merck Forms 10-K FY2023 and FY2025, product sales note
Steady, with a first dip in 2025.

The franchise is steady rather than spectacular. ProQuad, M-M-R II and Varivax together sold $2,135 million in 2021, $2,241 million in 2022, $2,368 million in 2023, $2,485 million in 2024 and $2,451 million in 202523. The small dip in 2025 is the first in the series.

The buyer is concentrated too. A large component of pediatric and adolescent vaccine sales is made to the Centers for Disease Control and Prevention's Vaccines for Children programme4, which the Major Clients page covers. When the customer is also the body that writes the schedule, the moat depends partly on policy.

Policy moved in 2025. The CDC's advisory committee recommended that children under four receive varicella protection as a standalone immunisation rather than in the combined MMRV shot5. Merck says it expects any negative effect on ProQuad sales not to be material6, and Varivax, which it also makes alone, benefits from the same change.

The same filing records a second schedule change nearby. In December 2025 the CDC ended the universal birth-dose recommendation for hepatitis B vaccination7. Merck's childhood vaccines are not all protected by being sole-source; the ones that are, ProQuad and Varivax, are protected against rivals but not against the recommendations that decide the size of the market.

Being the sole American producer is a durable, narrow advantage. The combined sales line, $2,451 million in 20258, is the number to follow; a second consecutive decline would say schedule changes are costing more than Merck expected.

Moat trajectory: Holding steady

Sales steady near $2.4-2.5bn; the 2025 dip is the first.

The number that tests this moat
Reported
ProQuad, M-M-R II and Varivax sales, full year
$2,451M (2025), against $2,485M in 2024

The childhood franchise; a second decline would mean schedule changes cost more than Merck expects.

Source: Merck Form 10-K, FY2025 ↗
⚠ Threats to the moat
⚠ THREAT 01
The CDC Split the MMRV Shot
Merck makes both the combined and the separate childhood shots, so the 2025 schedule change moved sales rather than removing them.
References
  1. ReportedMerck states that it is the only manufacturer in the United States of the combined measles, mumps, rubella and varicella vaccine, ProQuad, and of the varicella vaccine, Varivax.
    Merck & Co. Form 10-K for fiscal 2025 - vaccines and China: Gardasil, the childhood and pneumococcal vaccines, and sales in China. — FY2025 · publ. 24 February 2026 · source ↗
  2. ReportedProQuad, M-M-R II and Varivax together sold $2,135 million in 2021, $2,241 million in 2022, $2,368 million in 2023, $2,485 million in 2024 and $2,451 million in 2025.
    Merck & Co. Form 10-K for fiscal 2025 - vaccines and China: Gardasil, the childhood and pneumococcal vaccines, and sales in China. — FY2025 · publ. 24 February 2026 · source ↗
  3. ReportedProQuad, M-M-R II and Varivax together sold $2,135 million in 2021, $2,241 million in 2022, $2,368 million in 2023, $2,485 million in 2024 and $2,451 million in 2025.
    Merck & Co. Form 10-K for fiscal 2023 - product sales for 2021-2023, the Prometheus, Daiichi Sankyo and Imago charges, impairments, receivables concentration and the Zhifei distribution arrangement in China. — FY2023 · publ. February 2024 · source ↗
  4. ReportedA large component of pediatric and adolescent vaccine sales is made to the Centers for Disease Control and Prevention's Vaccines for Children programme, which the Major Clients page covers.
    Merck & Co. Form 10-K for fiscal 2025 - vaccines and China: Gardasil, the childhood and pneumococcal vaccines, and sales in China. — FY2025 · publ. 24 February 2026 · source ↗
  5. ReportedThe CDC's advisory committee recommended that children under four receive varicella protection as a standalone immunisation rather than in the combined MMRV shot.
    Merck & Co. Form 10-K for fiscal 2025 - Item 1A risk factors, patents and exclusivity, government pricing, vaccine policy and legal proceedings. — FY2025 · publ. 24 February 2026 · source ↗
  6. ReportedMerck says it expects any negative effect on ProQuad sales not to be material, and Varivax, which it also makes alone, benefits from the same change.
    Merck & Co. Form 10-K for fiscal 2025 - vaccines and China: Gardasil, the childhood and pneumococcal vaccines, and sales in China. — FY2025 · publ. 24 February 2026 · source ↗
  7. ReportedIn December 2025 the CDC ended the universal birth-dose recommendation for hepatitis B vaccination.
    Merck & Co. Form 10-K for fiscal 2025 - Item 1A risk factors, patents and exclusivity, government pricing, vaccine policy and legal proceedings. — FY2025 · publ. 24 February 2026 · source ↗
  8. ReportedThe combined sales line, $2,451 million in 2025, is the number to follow; a second consecutive decline would say schedule changes are costing more than Merck expected.
    Merck & Co. Form 10-K for fiscal 2025 - Item 1A risk factors, patents and exclusivity, government pricing, vaccine policy and legal proceedings. — FY2025 · publ. 24 February 2026 · source ↗
Sources
Generated September 25, 2026