Sanofi SNY and partner Translate Bio TBIO announced that they have initiated a phase I study which is evaluating their investigational, mRNA-based vaccine candidate against seasonal influenza.The study, which will be conducted in the United States, will investigate the safety and immunogenicity of the monovalent (single-strain) mRNA-based flu vaccine candidate in up to 280 participants. Initial data from the same is expected by the end of 2021.The companies will evaluate two formulations of the influenza mRNA vaccine (MRT5400 and MRT5401) in the phase I study. The study will evaluate several dose levels of both vaccine formulations given to healthy adults aged 18 to 49 years.The companies decided to begin the phase I study on the influenza vaccine candidate after it demonstrated promising safety and immunogenicity results in preclinical studies.Shares of Sanofi have rallied 7.7% so far this year compared with the industry’s growth of 8%.Image Source: Zacks Investment ResearchNotably, the study on the influenza vaccine candidate is the second mRNA vaccine program which has been undertaken by Sanofi and Translate Bio.We remind investors that Sanofi has also partnered with Translate Bio to develop a mRNA-based vaccine candidate, MRT5500, for treating COVID-19 infection. The candidate is currently being evaluated in a phase I/II study which is assessing its safety, immune response and reactogenicity.Meanwhile, Sanofi is also making an adjuvanted recombinant protein-based COVID-19 vaccine candidate in partnership with Glaxo GSK. The vaccine is being developed by combining Sanofi’s recombinant protein-based technology with Glaxo’s pandemic adjuvant technology.Last month, Sanofi/Glaxo began a pivotal phase III study on their adjuvanted recombinant protein-based COVID-19 vaccine candidate.The phase III study on the COVID-19 vaccine candidate follows the encouraging interim data from a phase II study announced in May 2021, in which the vaccine candidate demonstrated strong neutralizing antibody responses in all adult age groups, with 95 to100% seroconversion rates.Sanofi and Glaxo anticipate an approval for their vaccine candidate in the fourth quarter of 2021, subject to late-stage study data readout and regulatory review.Incidentally, Sanofi is lagging in its COVID-19 vaccine development efforts. Pfizer/BioNTech, Moderna MRNA, AstraZeneca and J&J have already launched their COVID-19 vaccines in several countries and vaccinations are in full swing.Zacks RankSanofi currently has a Zacks Rank #3 (Hold). You can see the complete list of today’s Zacks #1 Rank (Strong Buy) stocks here.Breakout Biotech Stocks with Triple-Digit Profit PotentialThe biotech sector is projected to surge beyond $775 billion by 2024 as scientists develop treatments for thousands of diseases. They’re also finding ways to edit the human genome to literally erase our vulnerability to these diseases.Zacks has just released Century of Biology: 7 Biotech Stocks to Buy Right Now to help investors profit from 7 stocks poised for outperformance. Our recent biotech recommendations have produced gains of +50%, +83% and +164% in as little as 2 months. The stocks in this report could perform even better.See these 7 breakthrough stocks now>>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Sanofi (SNY): Free Stock Analysis Report GlaxoSmithKline plc (GSK): Free Stock Analysis Report Moderna, Inc. (MRNA): Free Stock Analysis Report Translate Bio, Inc. (TBIO): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research