Covid vaccines are 99.992% effective in stopping the recurrence of infections, CDC data shows

Cases of Covid-19 are extremely rare among people who are fully vaccinated, according to a new data analysis by the Centers for Disease Control and Prevention.

Residents wait in an observation area after receiving Covid-19 vaccines at a vaccination site in Richmond, California.

Among more than 75 million fully vaccinated people in the U.S., just around 5,800 people reported a “breakthrough” infection, in which they became infected with the pandemic coronavirus despite being fully vaccinated.

The numbers suggest that breakthroughs occur at the teeny rate of less than 0.008 percent of fully vaccinated people — and that over 99.992 percent of those vaccinated have not contracted a SARS-CoV-2 infection.

The figures come from a nationwide database that the CDC set up to keep track of breakthrough infections and monitor for any concerning signs that the breakthroughs may be clustering by patient demographics, geographic location, time since vaccination, vaccine type, or vaccine lot number. The agency will also be keeping a close eye on any breakthrough infections that are caused by SARS-CoV-2 variants, some of which have been shown to knock back vaccine efficacy.

So far, the vaccines appear to be highly effective at stopping the variants and are working as expected, according to the CDC’s analysis.

The vast majority of people in the US have been vaccinated with one of the mRNA vaccines, made by Moderna and Pfizer-BioNTech, which both had around 95 percent efficacy in Phase III clinical trials. Less than five percent of vaccinated people in the US have received the Johnson & Johnson adenovirus-based vaccine, which had a slightly lower efficacy of 72 percent in the US but is 100 percent effect on severe cases.

The extraordinary calculation that 99.992 percent of vaccinated people have not contracted the virus may reflect that they all simply have not been exposed to the virus since being vaccinated. Also, there are likely cases missed in reporting. Still, the data is a heartening sign.

“Covid-19 vaccines are effective and are a critical tool to bring the pandemic under control,” the agency said in its email. “To date, no unexpected patterns have been identified in case demographics or vaccine characteristics.”

Keep masking up for now
Many of the breakthroughs occurred in older people, who are well-known to be more vulnerable to Covid-19. More than 40 percent were in people ages 60 and above. However, the agency noted that there were breakthrough infections scattered through every age group that is currently eligible for vaccination.

“We see [breakthroughs] with all vaccines,” top infectious disease expert Anthony Fauci said in a press briefing earlier this week. “No vaccine is 100 percent effective, which means that you will always see breakthrough infections regardless of the efficacy of your vaccine.”

Vaccines can fail in some people because of a variety of factors, including immune status, health status, age, and medications they’re on. There’s also the possibility that something went wrong with the vaccines themselves, such as improper storage, delivery, or composition, Fauci explained.

“However,” Fauci added, “even if a vaccine fails to protect against infection, it often protects against serious disease.” He highlighted the case of the 2019-2020 flu vaccine, which was only about 39 percent effective. Despite this, and the fact that only about 52 percent of people got their immunization, the vaccine was estimated to have prevented 105,000 flu hospitalizations and 6,300 flu deaths.

In the CDC’s data on breakthrough Covid-19 infections, the agency found that 29 percent of the infections were asymptomatic. Only seven percent of the 5,800 breakthrough cases resulted in hospitalization and there were only 74 deaths. That suggests the death rate among breakthrough cases is around one percent and, among all fully vaccinated people, around 0.0001 percent.

Though the risk is small, there is still risk. The CDC emphasized that everyone should get vaccinated when its their turn and, once vaccinated, should continue following health precautions for now, such as “wearing a mask, staying at least 6 feet apart from others, avoiding crowds and poorly ventilated spaces, and washing their hands often.”
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Credit: ARS Technica