Do COVID-19 breakthrough infections mean the vaccines are no longer effective?

(Tiếng Việt)

Claim: Due to the increased spread of the Delta variant, people who have been vaccinated have become infected with COVID-19, leading some to think that the vaccines are no longer effective against the virus.

Rating: This claim is FALSE. No vaccine is 100% effective at preventing infections. According to the Centers for Disease Control and Prevention (CDC), COVID-19 infections among the fully vaccinated (also called “breakthrough infections”) are to be expected. The more important fact is that the COVID-19 vaccines are still largely effective at preventing hospitalizations and deaths. Getting vaccinated and wearing a mask in public are still the most effective ways to prevent becoming infected with COVID-19

The Delta Variant Causes More Infections

The Delta variant is the current most common strain of COVID-19 in the U.S. With the Delta variant being nearly twice as contagious as the original strain of COVID-19, causing more infections and spreading faster than earlier forms of the virus, there has been an increased concern of what experts are calling “breakthrough infections” of COVID-19. 

According to the California Department of Public Health, from Jan. 01 to Sept. 12, 2021, 23.1 million Californians are fully vaccinated. Of those fully vaccinated people, 144,957 people were then infected with COVID-19, or 0.6% of vaccinated people.

Does this mean that the vaccines are no longer effective? According to public health officials, the answer is no

Vaccines Prevent Severe Illness and Death from COVID-19

Though the vaccines are highly effective in preventing COVID-19 infections, the main objective with vaccination was to prevent hospitalization and death. And the vaccines are still effective in that area. 

According to the state of California, out of the 144,957 people who were fully vaccinated and who became infected with COVID-19, only  3,751 people were hospitalized (0.2%). Among those vaccinated people who were infected with COVID-19, 500 died, though it is unknown whether they died of COVID-19 or some other causes. Yet 500 deaths out of 23.1 million people who were vaccinated points to the high protection of the vaccines. 

CDC data shows that the vaccine is highly effective in preventing hospitalizations and death. As of Sept. 13, 2021, more than 178 million people in the United States have been fully vaccinated against COVID-19. As of Sept. 13, there were 15,790 instances of vaccinated people who were hospitalized with COVID-19 or who died from COVID-19. That means that the percentage of people who are vaccinated and who have been hospitalized for COVID-19 is essentially zero.  

The data on breakthrough infections is limited. According to the CDC, since May 1, 2021, the organization “transitioned from monitoring all reported vaccine breakthrough cases to focus on identifying and investigating only hospitalized or fatal cases due to any cause.” This means the true number of breakthrough infections is unknown for people who have mild COVID-19 symptoms or no symptoms at all.

While much is unknown about asymptomatic or mild breakthrough infections, one thing is evident: The vaccines are still very effective at preventing hospitalizations and death. According to CDC data, the vast majority (98.9%) of people currently being hospitalized for COVID-19 are unvaccinated. The best way to protect yourself and those around you from COVID-19 is to get vaccinated. 

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Viet Fact Check has partnered with a number of community and health organizations to educate the Vietnamese-American community on the COVID-19 vaccine. The project is supported by: Progressive Vietnamese American Organization (PIVOT), Asian Health Services (AHS), the California Healthy Nail Salon Collaborative, Union of North American Vietnamese American Students (UNAVSA), Southeast Asian Resource Action Center (SEARAC), Asian American Research Center on Health (ARCH) and the Association of Asian Pacific Community Health Organizations (AAPCHO).

This article is supported by the Centers for Disease Control and Prevention of the U.S. Department of Health and Human Services (HHS) as part of a financial assistance award totaling $3,300,000 with 40% funded by CDC/HHS. The contents are those of the author(s) and do not necessarily represent the official views of, nor an endorsement, by CDC/HHS, or the U.S. Government.