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Meissa's Positive Interim Clinical Data for Its Intranasal Live Attenuated RSV Vaccine for Infants

Meissa Vaccines Announces Positive Interim Clinical Data for Its Intranasal Live Attenuated Respiratory Syncytial Virus (RSV) Vaccine Candidate for Infants

  • Meissa’s intranasal live attenuated RSV vaccine, MV-012-968, induced a strong systemic and mucosal IgA antibody response in RSV-naïve children

  • Safety data show that MV-012-968 is highly attenuated, with no serious adverse events reported and negligible vaccine virus shedding detected from any participants to date

  • No vaccine is currently approved for infants to protect against RSV; RSV is the leading cause of infant hospitalization in the United States and is considered a “missing” pediatric vaccine

  • MV-012-968 is the lead program from Meissa’s AttenuBlock(TM) platform; Meissa is also advancing a nasal live attenuated COVID-19 vaccine to protect against SARS-CoV-2

REDWOOD CITY, Calif., November 7, 2022 – Meissa Vaccines (“Meissa”), a clinical-stage biotechnology company developing vaccines to prevent viral respiratory infections, today announced interim clinical data of MV-012-968, Meissa’s intranasal live attenuated RSV vaccine candidate, from a Phase 1c study in RSV-naïve (seronegative) infants and young children. Meissa is developing MV-012-968 as a needle-free, adjuvant-free vaccine to protect infants and young children from RSV. The data will be presented today at the 7th International Conference on Vaccines Research & Development (R&D).

“We are extremely pleased with the data from this clinical study in RSV-naïve infants and young children because Meissa’s pediatric live attenuated RSV vaccine demonstrated outstanding immunogenicity while also showing high attenuation and excellent safety,” said Martin Moore, Ph.D., cofounder and Chief Scientific Officer, Meissa Vaccines. “Live attenuated vaccines have historically provided broad and durable protection. These data clinically validate our AttenuBlock platform's ability to generate live attenuated vaccines with outstanding immunogenicity and safety. Achieving both has previously been a major hurdle.”

The study enrolled 66 participants between the ages of six and 36 months at multiple sites in the U.S. to evaluate the safety and immunogenicity of MV-012-968 ( Identifier: NCT04909021). Meissa’s intranasal live attenuated RSV vaccine was well-tolerated with no safety concerns identified, no serious adverse events to-date, and negligible vaccine virus shedding. Solicited symptoms were generally mild and did not differ in incidence from the placebo group. At the highest dose regimen studied to date (two doses of 106 PFU), the vaccine stimulated a serum neutralizing antibody response in 78% of RSV-naïve children. Taken together with nasal IgA responses, the vaccine induced an immune response in 89% of RSV-naïve children.

Janet Englund, M.D., Professor, Department of Pediatrics, University of Washington School of Medicine, Seattle Children’s researcher, and a paid advisor to the company, stated, “Development of a live, attenuated RSV vaccine has been a decades-long effort with safety in naïve infants presenting a major stumbling block. The data support further study of Meissa’s investigational RSV vaccine. Having worked on RSV vaccine trials for many years, I am thrilled to see progress in the development of a vaccine for active immunization of young children.”

RSV is a leading cause of respiratory infections such as bronchiolitis and viral pneumonia in infants. In the United States, approximately 1% of infants are hospitalized because of RSV each year. Globally, in children under 5 years of age, RSV causes more than 66,000 deaths per year and approximately three million hospitalizations (Anderson 2013). Since the discovery of RSV in 1956, no vaccine has been approved for prevention.

“The development of a safe and effective RSV vaccine is a significant global health priority that could save thousands of lives and protect the health of millions of children around the world,” said Frank Glavin, Chief Executive Officer, Meissa Vaccines. “The clinical data we have generated from both our RSV and COVID-19 programs demonstrate the enormous potential of Meissa’s AttenuBlock platform to develop safe and effective intranasal live attenuated vaccines to protect against serious respiratory viruses, and we look forward to continuing to advance our vaccine candidates in clinical trials.”

About Meissa’s Intranasal Live Attenuated RSV Vaccine Candidate

Meissa is developing MV-012-968, an intranasal (needle-free), adjuvant-free, live attenuated vaccine candidate, to protect infants from respiratory syncytial virus (RSV). MV-012-968 was generated using the company’s proprietary AttenuBlock(TM) synthetic biology platform with the goal of creating safe, potent, stable, and cost-effective intranasal vaccines.

About AttenuBlock(TM): Meissa’s Intranasal Vaccine Platform

Meissa’s live attenuated intranasal vaccines for RSV and SARS-CoV-2 (COVID-19) are built on the company’s proprietary AttenuBlock platform to achieve appropriate attenuation, genetic stability, and optimized immunity. Injectable vaccines typically induce only serum (IgG) antibodies that circulate in the blood and are important for preventing serious lung disease. Intranasal vaccines generate serum IgG and mucosal (IgA) antibodies in the nasal cavity, which are essential for blocking infection and transmission of respiratory viruses, like RSV and SARS-CoV-2. Meissa’s vaccine platform and intranasal vaccine strategy are uniquely designed to confer mucosal immunity that will likely reduce transmission, if compared to injectable vaccines, provide long-lasting protection, and be a part of the global solution to controlling respiratory viruses.

About Meissa Vaccines

Meissa Vaccines was founded with a mission to protect people everywhere from life-threatening respiratory viruses and a commitment to develop innovative technologies capable of delivering effective vaccines at a global scale. Meissa is advancing intranasal, live attenuated vaccine candidates against respiratory syncytial virus (RSV), SARS-CoV-2 (COVID-19), and human metapneumovirus (hMPV). These vaccine candidates have been developed using the company’s proprietary AttenuBlock(TM) platform, which includes codon deoptimization and technologies exclusively licensed from Emory University and Children’s Healthcare of Atlanta. Meissa’s live attenuated vaccine candidates are formulated to be delivered as an adjuvant-free, needle-free dose and are designed to generate a strong, durable immune response to prevent infection and disease. Meissa is headquartered in Redwood City, California. For more information, please visit

Meissa Contacts:

Corporate Contact: Frank Glavin, CEO, Meissa Vaccines,

For Media Only: Jessica Yingling, Ph.D.,Little Dog Communications Inc.,, +1.858.344.8091


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