Fact or Fiction?
Effectiveness
FACT: Vaccines are very effective and work well to prevent illness.
Effectiveness is a measurement that shows how successful a vaccine is at preventing illness and death.
Vaccine effectiveness tells you how many fewer cases there will be within a population if an individual contracts a vaccine-preventable disease. Most childhood vaccines are over 90% effective at protecting against disease. That’s quite high! Although they are not 100% effective, vaccines are still worthwhile. Vaccines act like a car seat. A car seat cannot guarantee a child will never be harmed in a car crash. But, it can greatly reduce their likelihood of being hurt. Vaccines are not guaranteed to prevent illness, but they can provide high levels of protection.
Scientists study vaccines to measure their effectiveness.
To measure vaccine effectiveness, scientists test how well a vaccine works in controlled studies and in the real world. They determine if the vaccine can prevent infection, illness, hospitalization, and even death.
Typically, two types of research studies are used: randomized controlled trials (RCTs) and observational studies. In RCTs, two groups of volunteers are randomly assigned, one to get the vaccine and one to get a placebo. A placebo is a substance that has no medicinal effect. The researchers then monitor how many participants from each group get the disease. This helps determine if the vaccine is effective at preventing the disease. RCTs, a type of “clinical trial,” are required by the Food and Drug Administration (FDA) before any vaccine is licensed to be used by the public. Observational studies measure vaccine effectiveness in various real-world scenarios. These allow researchers to understand how vaccines work in different settings and among people of different ages with different medical conditions. Researchers again compare how many vaccinated and unvaccinated people get the disease. RCT’s are done in a controlled situation. Observational studies help us learn how effective vaccines are in the real world.
How was COVID-19 vaccine effectiveness in children measured?
For COVID-19 vaccines, researchers conducted clinical studies similar to RCT’s in each age group. For 5–11-year-olds. They tracked if any children were infected with COVID-19 after they were vaccinated. Researchers found that 3 out of 1,305 vaccinated children got COVID-19. 16 out of 663 children given the placebo got COVID-19. These results show that the vaccine is around 91% effective at preventing COVID-19 infections for 5 – 11 year olds.
Similar studies were done for other age groups with each vaccine type. These found that effectiveness was usually around 90%.
Remember, no vaccine is 100% effective, so it is still possible for a vaccinated person to get COVID-19. However, symptoms will generally be less severe for people who have been vaccinated, especially if in the last few months. Since they are vaccinated, they are less likely to be hospitalized with or die from COVID. Vaccinated people are also contagious for a shorter period of time.
The CDC regularly monitors COVID-19 vaccines and all other vaccines. They work with public health officials and academics to conduct observational studies. Because of these scientific studies and continuous monitoring, we know that the COVID-19 vaccines are safe and effective for everyone aged 6 months and older. Vaccination against COVID-19 gives you and your loved ones protection from a deadly disease.
How is influenza (flu) vaccine effectiveness measured?
The flu virus changes each flu season, which is why we get a yearly flu shot. Each year, scientists try to match the vaccine as closely to the circulating virus strains as possible. This is hard to do, but most years, the influenza vaccine reduces the risk of getting the flu by 40-60%.
Healthy children and adults can still get severely sick from the flu. Every year, 100-200 children 0-17 years old will die from influenza. Older adults, young children, and people with certain medical conditions have a higher risk of severe illness from the flu. Getting an annual flu vaccine is the best way to reduce your risk of getting the flu. Some people who get a flu vaccine may still get sick. But, the vaccine reduces the chance of severe illness, hospitalization, and flu-related death.
The effectiveness of flu vaccines can vary, but they are still the best way to protect against flu.
Vaccines help protect against severe complications from diseases.
The bottom line is that vaccines are effective. While no medicine is 100% effective, vaccines greatly reduce the risk of hospitalization and death if you do get sick. Routine vaccination has prevented and continues to prevent hundreds of millions of illnesses from vaccine-preventable diseases. If we stop vaccinating, we will quickly see an increase in these vaccine-preventable diseases.