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Testing the safety and efficacy of a vaccine
Vaccines work by causing the body’s immune system to make proteins, called antibodies, that fight disease, but without giving a person the disease.
Before a vaccine can be approved for use in the general public, it usually goes through clinical safety trials which can last from 2 to 15 years. The U.S. government’s Operation Warp Speed accelerated this process in an unprecedented way, in large part because it invested $ 18 billion up front to help create lab spaces, build infrastructure, invest in research and pre-purchase vaccines. In December 2020, healthcare workers in the United States began receiving the first COVID-19 vaccines authorized for adults.
Vaccine studies begin with laboratory experiments, where candidate vaccines are developed and tested in animals. After drug companies and government labs do the initial testing on candidate vaccines, they then turn to research groups across the country and around the world to conduct multiple phases of human clinical trials.
In phase 1 trials, the main objective is to establish the safety of the vaccine in humans. In phase 2, researchers continue to assess the safety of the vaccine, but with the goal of determining the exact dosage needed to elicit the immune response needed to confer protection. Once a vaccine candidate enters Phase 3 trials, the primary objective is to study the extent to which people are protected against infection or disease, while continuing to assess safety and monitor potential side effects.
Once clinical trials are completed, vaccines still have to undergo a rigorous evaluation process through the United States Food and Drug Administration, the regulatory body that oversees the safety and efficacy of vaccines.
After tens of thousands of adults participated in phase 3 clinical research studies of COVID-19 vaccines over several months in 2020 and early 2021, the United States now has three vaccines licensed for use emergency by the FDA for persons 18 years of age and older and a vaccine, Pfizer, cleared for use in children 12 years of age and older.
How children’s bodies differ from adults’
Children are not just smaller adults; their bodies differ significantly from adults.
Their brains are developing rapidly and their immune systems also have important differences, especially in toddlers and babies. During the first months of life, the immune system of infants still has the antibodies they received from their mother through the placenta during late pregnancy. This changes the way newborns respond to pathogens and makes them less able to develop an immune response to certain vaccines. Young children’s bodies gradually strengthen their own immune systems as their protection against the mother wears off.
Vaccines therefore often need to be tailored specifically for young children. For example, the pneumococcal vaccine that prevents infections like pneumonia in adults is made from sugar molecules called polysaccharides, which coat the outside of pneumococcal bacteria. But infants cannot develop an effective immune response against these sugar molecules. The researchers therefore had to develop a unique version of the vaccine for babies.
Even when an adult vaccine is found to be safe in children, there can be significant differences in how their bodies respond to it. The dose of vaccine that works best in adults can cause a high fever in children, for example. Thus, one of the key goals of clinical trials of the COVID-19 vaccine in children will be to determine the optimal dosage for each age group.
Researchers need to be alert to side effects that might occur only in young people and that do not show up in vaccination tests on adults. Security is essential, and every study has many layers of security mechanisms in place to ensure that researchers like us proceed with caution and assess all data and information every step of the way.
For example, trial participants keep a daily diary and report any side effects or changes. Clinical vaccine trials include frequent safety checks with participants, and unusual reactions are reported immediately to the study sponsor so that any issues can be identified quickly. Researchers also adhere to strict “pause” rules if a serious safety issue arises.
Clinical trials for children
After setting up a new clinical trials space and gathering all the necessary staff and equipment, the trials unit here at the University of Pittsburgh was ready to host Phase 3 clinical trials with volunteer participants. .
From August 2020 through the fall, we conducted phase 3 clinical trials in adults for Moderna and Johnson & Johnson vaccines. We recently recruited children aged 6 to 11 as well as 6 to 24 months in Phase 2 of the Moderna pediatric trials, focusing on the safety of using the vaccine in these children and at what doses.
Our site is now on the verge of moving into Phase 3 pediatric trials, which are currently scheduled to begin in mid-August for children aged 6 to 11, in the United States and Canada. This final step in clinical trials will determine how well the vaccine actually works to prevent children from contracting COVID-19. We expect the first results from these studies by this fall, after which they will be reviewed by the FDA.
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The FDA said on July 15 that emergency clearance for vaccines for children under 12 is expected to arrive in early to mid-winter.
The vital role of volunteers in ending the pandemic
Volunteering for a research study is not for everyone.
When a family volunteers to enroll in a vaccine study, our research team has an in-depth discussion with them about the requirements, as well as the potential risks and benefits. We try to answer all of their questions so that they can decide if a study is right for them. Ultimately, parents are trying to make a decision that is in their child’s best interests.
Often our volunteers tell us they wanted to help end the pandemic or felt it was their personal responsibility to help others. Their willingness to participate is crucial in finding a safe and effective vaccine that will hopefully help end the pandemic and help parents – and children – regain the freedoms of life before the pandemic.
This article is republished from The Conversation, a nonprofit news site dedicated to sharing ideas from academic experts. It was written by: Judy Martin, University of Pittsburgh.
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Judy Martin works for the University of Pittsburgh which receives funding from the National Institutes of Health. The University of Pittsburgh receives funding from the National Institutes of Health to conduct research studies on SARS-CoV-2 vaccines.
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