A viral video tracks the decline in the reported effectiveness of COVID-19 over time, insinuating that early headlines about the vaccines being “100 percent effective” were disinformation. A social media CEO shared the video in a post that has been viewed over 70 million times. The CEO also claimed that the COVID-19 booster almost sent him to the hospital and argued against vaccine mandates. The viral video is highly misleading because it doesn’t distinguish between trial efficacy and real-world effectiveness, or between effectiveness against severe disease and effectiveness against infection.
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How is vaccine effectiveness determined?
There are two key measures that determine vaccine effectiveness: clinical trial efficacy and real-world effectiveness. Trial efficacy is measured in a structured clinical trial. These trials involve groups of diverse people and measure how much a vaccine reduces their risk of getting sick. If a vaccine has high efficacy, that means there were significantly fewer people in the vaccinated group who got sick compared with the unvaccinated group. Vaccine effectiveness measures successful immune protection under real-world conditions. If a vaccine has high effectiveness, there is real-world proof that the vaccine protects people against severe infection, symptomatic illness, hospitalization, and death.
While vaccine effectiveness can be quantified using percentages, without context these statistics can oversimplify the number of factors used to determine outcomes. Vaccine effectiveness varies based on location, population, research approach, and specific health outcomes. CDC and other public health researchers routinely monitor and evaluate data for vaccine effectiveness.
Are COVID-19 vaccines effective?
Yes, the COVID-19 vaccines are highly effective at reducing the risk of severe infection, symptomatic illness, hospitalization, and death by providing immune protection that lasts several months.
The original Moderna and Pfizer-BioNTech COVID-19 vaccines approved in December 2020 were both shown to have 95% efficacy in preventing symptomatic COVID-19 illness. These vaccines were also shown to have high efficacy, 93% and 88% efficacy respectively, in targeting the predominant strain and preventing hospitalization.
However, a vaccine can only protect against a strain that it recognizes. As the virus continues to circulate and mutate, new variants are less recognizable to our immune systems and may lead to new infections — even for people who are vaccinated. COVID-19 vaccine effectiveness wears off over time and the coronavirus is constantly evolving and mutating. As a result, updated vaccines have been developed to more closely target the currently circulating variants of concern and “boost” the public’s immune protection to avoid another wave of infections, hospitalizations, and deaths.
The updated Moderna and Pfizer-BioNTech vaccines that were approved in fall 2023 are critical in boosting the public’s COVID-19 immunity. According to the latest research data, the newly updated COVID-19 vaccines are effective at producing strong immune responses to new variants. The updated vaccines provide increased protection against currently circulating COVID-19 strains, especially those originating from the Omicron variant. Individuals who received the updated COVID-19 vaccines have shown antibody responses that were almost 10 to 17 times higher against subvariants than before their re-vaccination.
How were the COVID-19 vaccines developed so quickly?
It’s true that these specific vaccines were developed more quickly than most, but their development built upon many decades of work on coronavirus vaccines and mRNA technology.
The process included the same rigorous safety reviews that are required for all new vaccines. Scientists were able to develop the vaccines quickly, safely, and effectively because the urgency of the pandemic created greater access to research funding, reduced bureaucratic obstacles, and encouraged unparalleled levels of government and industry cooperation.
As new variants appear, vaccine researchers will continue to develop updated COVID-19 vaccines, also called “boosters,” to provide the highest level of protection against the virus.
Are COVID-19 vaccines safe?
Yes, COVID-19 vaccines are safe. The COVID-19 vaccines have been tested and monitored for safety more than any previous vaccine in U.S. history. All COVID-19 vaccines have been rigorously tested and reviewed for human safety through a three-phase clinical trial process. Based on this thorough process, public health officials can make evidence-based recommendations to keep the public safe.
More than 150,000 people participated in U.S. vaccine clinical trials, and almost 700 million vaccine doses have been safely administered in the U.S., with rare instances of adverse reactions. To ensure the continued safety of COVID-19 vaccines, data from clinical trials will continue to be collected for two years after each vaccine is first administered to ensure that they are safe over the long term. As with all vaccines, there will be ongoing monitoring for adverse events among people who are vaccinated in the future.
What is the risk of having a severe adverse reaction to the COVID-19 vaccine?
The risk of having a serious adverse reaction to the COVID-19 vaccine is very low — far lower than the risk of contracting COVID-19.
Common reactions to COVID-19 vaccination include mild side effects, such as limb soreness, fatigue, low-grade fever, headaches, and chills, which typically resolve within a few days.
Severe adverse reactions after vaccination are extremely rare, but can cause long-term health issues. Adverse events, such as anaphylaxis and other allergic reactions, blood-clotting syndromes, heart inflammation, autoimmune diseases impacting the nervous system, and death, have been reported within the Vaccine Adverse Event Reporting System (VAERS).
If you have a question about the risks associated with vaccines, talk with your healthcare provider.
Am I permanently immune after getting vaccinated? What about breakthrough infections?
Given that COVID-19 is an evolving virus, researchers and medical experts continue to monitor how long vaccines provide immunity, which groups may benefit from additional doses, and how well the vaccines protect against new variants of the virus.
COVID-19 vaccines, like all other vaccines, do not provide 100% immunity. But they have been shown to be extremely effective in preventing serious illness, and they provide continued protection during periods of peak respiratory virus spread, such as the fall and winter months.
“Breakthrough” COVID-19 infections refer to infections in people who have fully completed the recommended vaccination schedule. This type of infection is not uncommon and can occur for multiple reasons. With the benefit of protection from the COVID-19 vaccine, breakthrough infections typically produce mild symptoms and do not require hospitalization. People who are not vaccinated continue to account for the vast majority of severe cases, hospitalizations, and deaths from COVID-19.
COVID-19 vaccines are a very important tool to protect against serious health outcomes, however vaccination alone is not enough to protect the public. It is also encouraged to practice other precautionary measures such as wearing a mask, covering a sneeze with a bent elbow or tissue, handwashing, avoiding crowded and closed spaces, social distancing from others, and isolating when sick.
Those who have compromised immune systems particularly benefit from practicing all recommended health precautions, including being vaccinated.
If you have questions about your risk of COVID-19, how to protect yourself, or the vaccines, consult with your healthcare provider.
Can my school or work mandate COVID-19 vaccination?
Yes, your school or work can mandate the COVID-19 vaccine, with some exceptions. Schools or employers may require vaccinations for attendance or employment, and those requirements vary by state and employer.
While these requirements vary, the research remains the same: the best way to protect yourself from getting COVID-19 is to get vaccinated, and practice precautionary measures like handwashing, social distancing, wearing a mask, and isolating when sick.
Schools: All states have vaccination requirements for children attending school and childcare facilities. Vaccination requirements help safeguard children by making sure they are protected when they begin school, where there is a higher potential for transmission of some diseases. To learn more about vaccine requirements by state, visit the CDC’s SchoolVaxView Requirements Database.
Employers: On January 13, 2022, the Supreme Court ruled that the federal government cannot enforce a vaccine mandate for large businesses. This does not mean that private employers are blocked from creating vaccine mandates. Employers are still legally able to mandate COVID-19 vaccinations for employees.
Other Vaccine Requirements:
- As of June 5, 2023, the Omnibus COVID-19 Health Care Staff Vaccination interim final rule (IFR) was lifted. This means that workers and contractors at Medicare- and Medicaid-certified facilities are not required to be fully vaccinated against COVID-19.
- Private businesses may still require patrons to show proof of vaccination for entry, and these requirements vary by state and locality.
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