Merck Animal Health Announces Availability of Circumvent^® CL, a Ready-to-use Vaccine Protecting Pigs Against Porcine Circovirus Types 2a and 2d and Lawsonia intracellularis

December 12, 2025

New addition to Merck Animal Health’s swine portfolio offers convenient, all-in-one protection for pigs three weeks of age and older

RAHWAY, N.J., December 12, 2025 – Merck Animal Health, known as MSD Animal Health outside of the United States and Canada, a division of Merck & Co., Inc., Rahway, N.J., USA (NYSE:MRK), today announced the commercial availability of CIRCUMVENT^®CL vaccine, a ready-to-use vaccine formulated to protect pigs three weeks of age and older against disease caused by Porcine Circovirus (PCV) Types 2a and 2d and Lawsonia intracellularis.

CIRCUMVENT CL is designed to simplify herd health programs by delivering dual protection in a ready-to-use formulation that requires no mixing or reconstituting. This new product complements Merck Animal Health’s existing swine portfolio, including CIRCUMVENT CML, a single-dose, ready-to-use vaccine that protects against PCV Types 2a and 2d, Mycoplasma hyopneumoniae (M. hyopneumoniae) and Lawsonia intracellularis in pigs three weeks of age and older, which was introduced in 2023. CIRCUMVENT CL omits the mycoplasma component to meet the needs of herds that are now M. hyopneumoniae-negative while maintaining robust protection against PCV and Lawsonia intracellularis.

“Merck Animal Health is committed to delivering innovative, practical solutions that help veterinarians and producers protect herd health while streamlining on-farm operations,” said Brett O’Brien, V.M.D., swine technical services, Merck Animal Health. “CIRCUMVENT CL provides trusted protection against two of the most significant enteric and systemic disease agents impacting swine production in a ready-to-use formulation. By offering options such as CIRCUMVENT CML and CIRCUMVENT CL, we enable tailored vaccination strategies that simplify vaccine handling and administration.”

Key product benefits of CIRCUMVENT CL include:

Dual protection: Effective against disease caused by Porcine Circovirus Types 2a and 2d and Lawsonia intracellularis in pigs three weeks of age or older.
Ready-to-use: Single-bottle presentation requires no mixing or reconstituting, helping to reduce preparation time and potential handling errors.
Flexible herd options: Designed for use in herds where M. hyopneumoniae vaccination is not required, providing a targeted solution for M. hyopneumoniae-negative operations.
Complementary portfolio: Adds to Merck Animal Health’s CIRCUMVENT family, enabling veterinarians to choose the formulation that best fits herd health status and management goals.

CIRCUMVENT CL is available in 50- and 250-dose presentations. A 500-dose presentation will be available in Q1 2026. For more information, contact your Merck Animal Health sales or technical services representative or visit https://www.merck-animal-health-usa.com/species/swine.

Product Label

Merck Animal Health announces that CIRCUMVENT^®CL vaccine is commercially available as part of its swine portfolio. CIRCUMVENT CL is the first ready-to-use, single-dose vaccine effective against disease caused by Porcine Circovirus Types 2a and 2d and Lawsonia intracellularis in pigs, three weeks of age or older. CIRCUMVENT CL is available in 50- and 250-dose presentations. A 500-dose presentation will be available in Q1 2026.

About Merck Animal Health

At Merck, known as MSD outside of the United States and Canada, we are unified around our purpose: We use the power of leading-edge science to save and improve lives around the world. For more than a century, we’ve been at the forefront of research, bringing forward medicines, vaccines and innovative health solutions for the world’s most challenging diseases. Merck Animal Health, a division of Merck & Co., Inc., Rahway, N.J., USA, is the global animal health business of Merck. Through its commitment to The Science of Healthier Animals^®, Merck Animal Health offers veterinarians, farmers, producers, pet owners and governments one of the widest ranges of veterinary pharmaceuticals, vaccines and health management solutions and services as well as an extensive suite of connected technology that includes identification, traceability and monitoring products. Merck Animal Health is dedicated to preserving and improving the health, well-being and performance of animals and the people who care for them. It invests extensively in dynamic and comprehensive R&D resources and a modern, global supply chain. Merck Animal Health is present in more than 50 countries, while its products are available in some 150 markets. For more information, visit
www.merck-animal-health.com and connect with us on LinkedIn, Facebook, X (formerly Twitter) and Instagram.

Forward-Looking Statement of Merck & Co., Inc., Rahway, N.J., USA

This news release of Merck & Co., Inc., Rahway, N.J., USA (the “company”) includes “forward-looking statements” within the meaning of the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995. These statements are based upon the current beliefs and expectations of the company’s management and are subject to significant risks and uncertainties. If underlying assumptions prove inaccurate or risks or uncertainties materialize, actual results may differ materially from those set forth in the forward-looking statements.

Risks and uncertainties include but are not limited to, general industry conditions and competition; general economic factors, including interest rate and currency exchange rate fluctuations; the impact of pharmaceutical industry regulation and health care legislation in the United States and internationally; global trends toward health care cost containment; technological advances, new products and patents attained by competitors; challenges inherent in new product development, including obtaining regulatory approval; the company’s ability to accurately predict future market conditions; manufacturing difficulties or delays; financial instability of international economies and sovereign risk; dependence on the effectiveness of the company’s patents and other protections for innovative products; and the exposure to litigation, including patent litigation, and/or regulatory actions.

The company undertakes no obligation to publicly update any forward-looking statement, whether as a result of new information, future events or otherwise. Additional factors that could cause results to differ materially from those described in the forward-looking statements can be found in the company’s Annual Report on Form 10-K for the year ended December 31, 2023 and the company’s other filings with the Securities and Exchange Commission (SEC) available at the SEC’s Internet site (www.sec.gov).