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For life and breath.

Live Attenuated Vaccines for Life-Threatening Respiratory Viruses

Respiratory viruses are one of the biggest threats to human health. Vaccines are the most effective healthcare tool to combat infectious diseases and have saved more lives than any other type of medicine. Meissa is dedicated to creating safe, potent, stable, and accessible intranasal live attenuated vaccines that can prevent infection and disease. Meissa’s RSV and COVID-19 live attenuated vaccine candidates were developed using the company’s AttenuBlock platform.

Meissa’s Vaccine Pipeline

Meissa’s pipeline of live attenuated vaccine candidates are being developed to protect against respiratory syncytial virus, SARS-CoV-2, human metapneumovirus, and parainfluenza virus.

Our Intranasal Vaccines Induce Both Mucosal and Circulating Antibodies

Intranasal vaccines generate both mucosal (IgA) antibodies in the nasal cavity and antibodies that circulate in the blood (serum). In contrast, injected vaccines typically induce circulating but not mucosal antibodies. While circulating antibodies are important for preventing serious lung disease, mucosal antibodies are important for blocking infection by incoming respiratory viruses. If infection is fully blocked, there is no viral replication and no transmission of virus to another person. The potential to prevent viral transmission is a key advantage that intranasal vaccines have versus injected vaccines.


In a Phase 1 clinical trial, Meissa’s RSV vaccine candidate stimulated a strong mucosal IgA response in adults who already had circulating antibodies to RSV in their blood. These results were consistent with previous animal studies, in which Meissa’s RSV vaccine candidate stimulated strong mucosal IgA antibody and circulating antibody responses and prevented infection of both the upper and lower respiratory tracts. Collectively, these results warrant further development of our vaccine candidates by demonstrating both mucosal and systemic immunity that blocks infection and prevents disease. 

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Meissa's RSV Live Attenuated Vaccine Candidate

In a Phase 1 clinical trial, Meissa’s RSV vaccine candidate was safe and well-tolerated among healthy RSV sero-low adults ( Identifier NCT04227210). A single dose of our RSV vaccine candidate resulted in no detectable vaccine virus being shed nasally, indicating heavy attenuation, and yet induced RSV-specific mucosal IgA in the majority of vaccine recipients, despite pre-existing immunity to RSV. These results differentiate Meissa’s RSV vaccine candidate from other live attenuated RSV vaccine candidates. Meissa’s RSV vaccine candidate is currently being tested in a Phase 1 trial in seropositive children ( Identifier NCT04444284).


About RSV 


Respiratory syncytial virus (RSV) is the leading cause of infant hospitalization in the United States and is considered the “missing” mandatory pediatric vaccine. RSV is also a significant cause of morbidity and mortality in older adults. In the United States, approximately 1% of infants are hospitalized by RSV each year.  Globally, RSV causes more than 66,000 deaths per year and approximately 3 million hospitalizations in children less than five years of age (Anderson 2013).

Meissa’s COVID-19 Live Attenuated Vaccine Candidate

Meissa is developing a live attenuated COVID-19 vaccine candidate, to induce immunity and protect against SARS-CoV-2, the novel coronavirus that causes COVID-19. Like its RSV vaccine candidate, Meissa’s COVID-19 vaccine candidate offers significant potential advantages for global deployment, including needle-free intranasal administration, a single adjuvant-free dose to induce mucosal and systemic immunity, as well as a straightforward, economical, and scalable manufacturing process. Clinical trials are expected to begin in early 2021.

To stay informed about our clinical progress for our our RSV and COVID-19 vaccine candidates, sign up for our e-updates.


Meissa Vaccines, Inc.

© 2020 Meissa Vaccines, Inc.