From genome sequencing to tissue engineering, the medical world is constantly evolving. In recent years, significant advancements have been made to combat influenza. Every year, scientists develop a new flu vaccine to combat that season’s strains of the virus. In the following, we examine the process involved in developing flu vaccines.
What Is the Process of Developing a Vaccine?
Developing a vaccine can be an arduous, complex process that sometimes takes decades. Vaccines are heavily regulated and must undergo stringent testing before becoming available to the general public.
The development of new vaccines generally consists of five key stages.
Exploratory Stage—This stage, which generally lasts from two to four years, encompasses general laboratory research. Experts identify prospective antigens to fight or prevent a disease.
Pre-Clinical Stage—In the pre-clinical stage of development, the candidate vaccine is tested on animals to determine its efficacy and detect any possible side effects. Mice and monkeys are often used as subjects. At this stage, scientists often adapt the vaccine to improve its effectiveness. If a candidate vaccine fails to produce the desired response, researchers will abandon development. The pre-clinical stage can take up to two years to complete.
Applying for FDA approval—A sponsor applies to the FDA for Investigational New Drug approval. In the application, the sponsor identifies manufacturing processes and summarizes laboratory reports, as well as the objectives of the proposed study. The FDA has up to 30 days to assess the application. If an application is successful, then the vaccine can move on to the next phase of testing.
Clinical Trials—After a candidate vaccine has received FDA approval, researchers can test it on humans. Vaccine trials generally consist of three key phases. In Phase 1 testing, researchers test the vaccine on a small number of individuals, usually between 20 to 80 adults. When researchers are developing a children’s vaccine, they first test it on adults, then gradually descend in age group until they reach their target. The conditions are carefully controlled, and participants are closely monitored to gauge efficacy and any adverse side effects. In Phase 2 testing, researchers use a larger group. Some participants may belong to groups perceived to be at higher risk of developing the disease. Phase 2 testing involves monitoring the candidate vaccine’s safety and effectiveness. In addition, researchers will decide on the most effective way to deliver the vaccine and the necessary dose. Phase 3 trials frequently involve tens of thousands of participants, with some receiving the candidate vaccine and others a placebo. When testing a large cross-section of the population, rare side effects are sometimes detected that may have slipped through in earlier testing phases.
FDA Licensing—If researchers can prove that a vaccine is safe and effective in clinical trials, then the sponsor will apply to the FDA for a Biologics License. The FDA will conduct a factory inspection and approve the vaccine’s labeling. After licensing the vaccine, the FDA will continue to monitor its production, which will include inspecting the factory and testing vaccine samples for purity, safety, and potency. The United States government established the Vaccine Adverse Event Reporting System (VAERS) in 1990 as a way to report adverse events related to vaccines. Anyone can report a vaccine to VAERS, including a health care provider, patient, friend, or family member who suspects a link between the administration of the vaccination and an adverse event.
The Three Types of Flu Vaccines
There are three different types of flu vaccines available in the United States today.
Cell-Based Flu Vaccines—The development of cell-based flu vaccines involves introducing candidate vaccine viruses to mammalian cells to enable the vaccine cells to replicate. Scientists can then extract the vaccine from the host. After purifying and testing the vaccine, they will await FDA approval and licensing for release to the general public.
Egg Based Flu Vaccines—As the name suggests, scientists cultivate egg-based vaccines within hens’ eggs. Again, egg-based vaccines are subject to strict monitoring and approval by the FDA.
Recombinant Flu Vaccines—Recombinant flu vaccines are a relatively new innovation. The first recombinant flu vaccine received FDA approval for release to the general public in 2013. The flu vaccines rely on the use of recombinant technology, eliminating the need for egg or mammalian hosts in the vaccine production process.
How Effective Is the Flu Vaccine?
In regards to the effectiveness of the flu vaccine, studies undertaken by the CDC reveal a 40% to 60% reduction in flu cases in 2018 among those who received vaccinations. While the flu vaccine is generally more effective among healthy younger people than older individuals with weakened immune systems, vaccination offers life-saving protection. In another study, the CDC revealed that flu vaccines saved an estimated 40,000 lives in the United States between 2005 and 2014.