Merck and Sanofi's First and Only Six-in-One Pediatric Combination Vaccine Now Available in the United States

VAXELIStm (Diphtheria and Tetanus Toxoids and Acellular Pertussis, Inactivated Poliovirus, Haemophilus b Conjugate and Hepatitis B Vaccine), developed as part of a U.S.-based partnership between Merck (NYSE: MRK), known as MSD outside the United States and Canada, and Sanofi Pasteur, the global vaccines business unit of Sanofi, is now available in the U.S. VAXELIS is the first and only hexavalent (six-in-one) combination vaccine available in the U.S. indicated for active immunization to help prevent diphtheria, tetanus, pertussis, poliomyelitis, hepatitis B, and invasive disease due to Haemophilus influenzae type b. VAXELIS is approved for use as a 3-dose series in children 6 weeks through 4 years of age (prior to the 5^th birthday).

"Given the potential to reduce the number of shots by as many as three in the first six months of life, as compared to pentavalent vaccines plus hepatitis B or Haemophilus influenzae type b vaccines, VAXELIS represents an important option for healthcare professionals and parents," said Joanne Monahan, senior vice president, U.S. Vaccines, Merck. "Merck and Sanofi have been in contact with the major insurers and the appropriate pricing publications to notify them of the availability of VAXELIS, and we look forward to working with payers and providers to deliver this novel hexavalent vaccine to age-appropriate children. This news should also help to remind providers and parents of the importance of continuing routine vaccinations and recommended well visits."

On February 11, 2021, the U.S. Centers for Disease Control and Prevention's Advisory Committee included VAXELIS as a combination vaccine option in the CDC's Recommended Child and Adolescent Immunization Schedule. VAXELIS will be widely available in the U.S. through traditional public and private channels, including directly from Sanofi Pasteur via vaccineshoppe.com.

"As the first six-in-one vaccine in the U.S., VAXELIS is now available to help protect infants and children against diseases caused by six infectious agents. We are proud to offer this vaccine to healthcare professionals and the patients they serve," said Elaine O'Hara, Head of Sanofi Pasteur Commercial Operations North America. "Studies have shown that combination vaccines may help increase vaccination compliance and reduce disease burden by improving vaccine timeliness and coverage rates.

Do not administer VAXELIS to anyone with a history of severe allergic reaction to a previous dose of VAXELIS, any ingredient of VAXELIS, or any other diphtheria toxoid, tetanus toxoid, pertussis-containing vaccine, inactivated poliovirus vaccine, hepatitis B vaccine, or H. influenzae type b vaccine, anyone with a history of encephalopathy within 7 days of a pertussis-containing vaccine with no other identifiable cause, or anyone with a history of progressive neurologic disorder until a treatment regimen has been established and the condition has stabilized.

About Combination Vaccines

Combination vaccines take two or more vaccines that could be given individually and put them into a single shot. Combination vaccines have been a significant catalyst for change for the healthcare industry since their introduction more than 50 years ago. Public health authorities and leading professional associations generally recommend the use of combination vaccines over separate injections, when appropriate, including the American Academy of Pediatrics, The American Academy of Family Physicians, U.S. Centers for Disease Control and Prevention, The World Health Organization and others.

About VAXELIS

VAXELIS was developed as part of a U.S.-based partnership established in 1991 between Merck and Sanofi Pasteur and draws upon both companies' experience in the development, manufacturing and marketing of individual and combination vaccines. VAXELIS includes antigens for diphtheria, tetanus, pertussis (whooping cough), and poliomyelitis from Sanofi Pasteur and antigens for Haemophilus influenzae type b and hepatitis B from Merck.

VAXELIS is a vaccine indicated for active immunization to prevent diphtheria, tetanus, pertussis, poliomyelitis, hepatitis B, and invasive disease due to Haemophilus influenzae type b. VAXELIS is approved for use as a 3-dose series in children 6 weeks through 4 years of age (prior to the 5th birthday).

Important Safety Information for VAXELIS

Do not administer VAXELIS to anyone with a history of severe allergic reaction to a previous dose of VAXELIS, any ingredient of VAXELIS, or any other diphtheria toxoid, tetanus toxoid, pertussis-containing vaccine, inactivated poliovirus vaccine, hepatitis B vaccine, or H. influenzae type b vaccine.

Do not administer VAXELIS to anyone with a history of encephalopathy within 7 days of a pertussis-containing vaccine with no other identifiable cause.

Do not administer VAXELIS to anyone with a history of progressive neurologic disorder until a treatment regimen has been established and the condition has stabilized.

Carefully consider benefits and risks before administering VAXELIS to persons with a history of fever of ?40.5°C (?105°F), hypotonic-hyporesponsive episode (HHE), or persistent, inconsolable crying lasting ?3 hours within 48 hours after a previous pertussis-containing vaccine; and/or seizures within 3 days after a previous pertussis-containing vaccine.

If Guillain-Barré syndrome occurred within 6 weeks of receipt of a prior vaccine containing tetanus toxoid, the risk for Guillain-Barré syndrome may be increased following VAXELIS.

Apnea following intramuscular vaccination has been observed in some infants born prematurely. Consider the individual infant's medical status and potential benefits and possible risks of intramuscular vaccination in deciding when to administer VAXELIS to an infant born prematurely.

Vaccination with VAXELIS may not protect all individuals.

The solicited adverse reactions 0-5 days following any dose were irritability (?55%), crying (?45%), injection site pain (?44%), somnolence (?40%), injection site erythema (?25%), decreased appetite (?23%), fever ?38.0°C (?19%), injection site swelling (?18%), and vomiting (?9%).

The 3-dose immunization series consists of a 0.5 mL intramuscular injection, administered at 2, 4, and 6 months of age.

A 3-dose series of VAXELIS does not constitute a primary immunization series against pertussis; an additional dose of pertussis-containing vaccine is needed to complete the primary series.

Please see Prescribing Information for VAXELIStm (Diphtheria and Tetanus Toxoids and Acellular Pertussis, Inactivated Poliovirus, Haemophilus b Conjugate and Hepatitis B Vaccine) at https://www.merck.com/product/usa/pi_circulars/v/vaxelis/vaxelis_pi.pdf and Patient Information for VAXELIStm at https://www.merck.com/product/usa/pi_circulars/v/vaxelis/vaxelis_ppi.pdf.

About Merck

For 130 years, Merck, known as MSD outside of the United States and Canada, has been inventing for life, bringing forward medicines and vaccines for many of the world's most challenging diseases in pursuit of our mission to save and improve lives. We demonstrate our commitment to patients and population health by increasing access to health care through far reaching policies, programs and partnerships. Today, Merck continues to be at the forefront of research to prevent and treat diseases that threaten people and animals ? including cancer, infectious diseases such as HIV and Ebola, and emerging animal diseases ? as we aspire to be the premier research-intensive biopharmaceutical company in the world. For more information, visit www.merck.com and connect with us on Twitter, Facebook, Instagram, YouTube and LinkedIn.

About Sanofi

Sanofi is dedicated to supporting people through their health challenges. We are a global biopharmaceutical company focused on human health. We prevent illness with vaccines, provide innovative treatments to fight pain and ease suffering. We stand by the few who suffer from rare diseases and the millions with long-term chronic conditions.

With more than 100,000 people in 100 countries, Sanofi is transforming scientific innovation into healthcare solutions around the globe.

Sanofi, Empowering Life.

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

This news release of Merck & Co., Inc., Kenilworth, 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. There can be no guarantees with respect to pipeline products that the products will receive the necessary regulatory approvals or that they will prove to be commercially successful. 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 the global outbreak of novel coronavirus disease (COVID-19); 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 2020 Annual Report on Form 10-K and the company's other filings with the Securities and Exchange Commission (SEC) available at the SEC's Internet site (www.sec.gov).

Sanofi Forward-Looking Statements

This press release contains forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995, as amended. Forward-looking statements are statements that are not historical facts. These statements include projections and estimates and their underlying assumptions, statements regarding plans, objectives, intentions and expectations with respect to future financial results, events, operations, services, product development and potential, and statements regarding future performance. Forward-looking statements are generally identified by the words "expects", "anticipates", "believes", "intends", "estimates", "plans" and similar expressions. Although Sanofi's management believes that the expectations reflected in such forward-looking statements are reasonable, investors are cautioned that forward-looking information and statements are subject to various risks and uncertainties, many of which are difficult to predict and generally beyond the control of Sanofi, that could cause actual results and developments to differ materially from those expressed in, or implied or projected by, the forward-looking information and statements. These risks and uncertainties include among other things, the uncertainties inherent in research and development, future clinical data and analysis, including post marketing, decisions by regulatory authorities, such as the FDA or the EMA, regarding whether and when to approve any drug, device or biological application that may be filed for any such product candidates as well as their decisions regarding labelling and other matters that could affect the availability or commercial potential of such product candidates, the fact that product candidates if approved may not be commercially successful, the future approval and commercial success of therapeutic alternatives, Sanofi's ability to benefit from external growth opportunities, to complete related transactions and/or obtain regulatory clearances, risks associated with intellectual property and any related pending or future litigation and the ultimate outcome of such litigation, trends in exchange rates and prevailing interest rates, volatile economic and market conditions, cost containment initiatives and subsequent changes thereto, and the impact that COVID-19 will have on us, our customers, suppliers, vendors, and other business partners, and the financial condition of any one of them, as well as on our employees and on the global economy as a whole. Any material effect of COVID-19 on any of the foregoing could also adversely impact us. This situation is changing rapidly and additional impacts may arise of which we are not currently aware and may exacerbate other previously identified risks. The risks and uncertainties also include the uncertainties discussed or identified in the public filings with the SEC and the AMF made by Sanofi, including those listed under "Risk Factors" and "Cautionary Statement Regarding Forward-Looking Statements" in Sanofi's annual report on Form 20-F for the year ended December 31, 2020. Other than as required by applicable law, Sanofi does not undertake any obligation to update or revise any forward-looking information or statements.