--- title: COVID-19 Breakthrough Infections: Should You Be Worried? description: CDC reports very low rates of so-called "breakthrough infections" among vaccinated people, further evidence that vaccines work very well. canonical: https://time.com/6052238/breakthrough-covid-19-infections-vaccinated/ author: Alice Park article:opinion: false article:content_tier: free article:published_time: 2021-05-28T13:32:40.000Z article:modified_time: 2026-10-14T09:12:09.003Z article:section: Health og:title: Why Infections Even After COVID-19 Vaccinations Shouldn’t Be Surprising og:description: CDC reports very low rates of so-called "breakthrough infections" among vaccinated people, further evidence that vaccines work very well. og:url: https://time.com/6052238/breakthrough-covid-19-infections-vaccinated/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt9dac4ba8b0ad6419/698a19f716d884131ec39675/GettyImages-1231820196.jpg?branch=production&width=1024&quality=75&auto=webp&crop=16:9 og:image:width: 1024 og:image:height: 576 og:image:alt: Signs posted at a FEMA COVID-19 vaccination site at the og:type: article twitter:card: summary_large_image twitter:title: Why Infections Even After COVID-19 Vaccinations Shouldn’t Be Surprising twitter:description: CDC reports very low rates of so-called "breakthrough infections" among vaccinated people, further evidence that vaccines work very well. twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt9dac4ba8b0ad6419/698a19f716d884131ec39675/GettyImages-1231820196.jpg?branch=production&width=1024&quality=75&auto=webp&crop=16:9 ---  # Why 'Breakthrough' Infections Even After COVID-19 Vaccinations Shouldn’t Be Surprising > Sponsored content. 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Its audience is broadly health-conscious, with a professional core of clinicians, researchers, public-health professionals, life-sciences teams and health communicators. ### Sources * TIME Newsletters: [time.com/newsletters](/c/time-nl-health-2026q3/newsletters?i=782992d7-c7ff-4790-8120-09a016474b14&cr=time-nl-health-2026q3-v1) ## Video: Making the COVID-19 Vaccine: A 50,000 step process [Watch (HLS stream): Making the COVID-19 Vaccine: A 50,000 step process](https://cdn.jwplayer.com/manifests/XGIqdw9j.m3u8) (7:28)  _Published 2021-04-18. Inside BioNTech's quest to vaccinate the world_  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent May 28, 2021 1:32 PM UTC Inside BioNTech's quest to vaccinate the world  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent May 28, 2021 1:32 PM UTC In a recent _Morbidity and Mortality Weekly Report_ (_MMWR_), researchers at the U.S. Centers for Disease Control (CDC) provide [the first wide-scale look](https://www.cdc.gov/mmwr/volumes/70/wr/mm7021e3.htm?s%5Fcid=mm7021e3%5Fw) at the number of so-called “breakthrough infections”—COVID-19 infections occurring in people who are vaccinated against the disease. Among more than 101 million people who were fully vaccinated in the U.S. during the study period from Jan. to April 30—meaning they were two weeks out from their last vaccine dose—10,262 cases of SARS-CoV-2 infection were reported by state and local health departments to the CDC. That works out to just 0.01% of vaccinated people with a confirmed infection, an “incredibly low rate,” says Dr. Carlos del Rio, professor of medicine in the division of infectious diseases at Emory University. “To me, this is just reassuring evidence that vaccines really work.” No vaccine is 100% effective in protecting people from infection. And indeed, the three vaccines currently authorized in the U.S.—from[ Pfizer-BioNTech](https://www.cdc.gov/mmwr/volumes/70/wr/mm7021e3.htm?s%5Fcid=mm7021e3%5Fw),[ Moderna](https://time.com/5922752/moderna-covid-19-vaccine-approved-fda-emergency-use/) and[ Johnson&Johnson-Janssen](https://time.com/5942737/johnson-and-johnson-covid-19-vaccine-fda-review/)—were authorized on the basis of their ability to protect people against symptoms of COVID-19, not infection. But in the months since the vaccines rolled out, scientists have documented that people who are vaccinated have lower rates of infection than those who are unvaccinated. In a previous _MMWR_, published in March, the CDC[ reported](https://time.com/5950829/vaccines-covid-19-infection-real-world-study/) that in a study of nearly 4,000 health care workers, the two mRNA vaccines made by Pfizer-BioNTech and Moderna, were 90% effective in protecting people from getting infected with SARS-CoV-2. And that protection is confirmed in a far larger population of people by the current report. About 27% of the breakthrough infections among the 101 million people vaccinated occurred among those who experienced no symptoms of COVID-19, about 10%, or 995 cases, were known to be hospitalized, and 2%, or 160 people, died. And among those who were hospitalized, nearly a third were hospitalized for something _other_ than COVID-19, and among those that died, about a fifth died of something other than COVID-19. “At the end of the day, I think this is very good news,” says del Rio. “And when breakthrough infections do occur, in general they don’t have serious clinical consequences. So I think in general this is incredibly reassuring.” Dr. Bonnie Maldonado, professor of pediatrics, epidemiology and population health at Stanford University and a member of the CDC committee that reviews vaccines and comes up with immunization recommendations, agrees. “Frankly I think the numbers are amazing. These are miracle vaccines, with better than 90% efficacy in clinical trials, a 0.01% breakthrough infection rate, and almost no severe illness out of 100 million people tracked. It’s about the best information I could expect,” she says. The CDC data also explored to a limited extent what role new variants of SARS-CoV-2, which spread more easily among people and can cause more severe illness, played in the breakthrough infections. Researchers genetically sequenced the virus from only about 5% of the breakthrough infection cases, however, so the data aren’t robust. But so far, it shows that slightly more than half of the infections could be traced to the most common variant, B.1.1.7 (the one [first identified in the U.K.](https://time.com/5929246/uk-coronavirus-third-wave/)), with a recently identified variant from California contributing to about a quarter of the infections. But since overall the percentage of breakthrough infections is small, the immunity produced by the vaccines still appears to be sufficient at protecting against infection with these variants, and, if infections do occur, they lead to less severe disease in many cases. The authors note that the infections reported could be an underestimate of actual breakthrough infections, since the reporting is voluntary, and because many people who are positive may not feel symptoms and therefore would not get tested and diagnosed. Still, based on experience with other vaccines, public health experts expect that the rate will remain low, given how effective the COVID-19 vaccines are in producing antibodies that neutralize the virus as well as longer lasting immune defenses. As a result of these new data, the CDC has told states and local health departments they no longer need to report all cases of breakthrough infections, and instead to just notify CDC when these cases result in hospitalization, severe disease or death. “These \[cases\] are the ones we’re most concerned about,” CDC director Dr. Rochelle Walensky said during a press briefing addressing the change. Maldonado says there isn’t much added value in continuing to ask for all breakthrough infections, particularly since so many appear to occur without any symptoms. The breakthrough cases resulting in hospitalization or death will, she says, serve as a canary in the coal mine for when vaccine protection might be waning for whatever reason. That could, potentially, simply happen as a result of time passing. “By the end of this year, most of the early people will have been vaccinated about a year, and we might have to rethink then what gets reported and what doesn’t get reported,” says Maldonado. “Because then the question is, will we start losing immunity a year out?” She says state and local health departments will continue tracking all new COVID-19 cases—just not reporting the milder ones to the CDC. If cases start going up, then health experts can investigate the data to see if it looks like vaccinated people are starting to get infected more, and if so, whether variants might be responsible. For now, says Maldonado, the concern should be about people who aren’t vaccinated. That’s where new infections are starting and spreading to cause the breakthrough cases. “The vaccine is 0% effective if you don’t get it,” she says. ## Transcript [00:01] oh yes yes i'm vaccinated yes [00:06] Very cool [00:10] yes [00:11] yeah [00:12] yes, I did [00:13] it was very cool to to know [00:15] okay I'm gonna be vaccinated with a vaccine that I know really from day one [00:26] I mean who can tell that they're part of the solution for such a pandemic situation [00:30] I guess only a few people can say that and I'm really happy to be part of that [00:51] If you've been vaccinated for COVID-19, chances are that you are benefiting from the science [00:56] happening here at the German biotech company BioNtech. [01:00] In December 2020 BioNtech in partnership with Pfizer [01:04] were the first to earn authorization to distribute their vaccine to the public [01:17] In March 2021 TIME spent a week watching how BioNtech makes a batch [01:22] of 8 million doses of the COVID-19 vaccine at their new manufacturing plant in Marburg [01:29] they expect to produce 1 billion doses a year [01:44] the pace of production has been breakneck from the start [01:48] So in 2020 I think we worked [01:51] at every holiday, I can remember Easter Saturday I was standing here pipetting [01:55] samples to have the results as soon as possible [01:59] and now 24-hour shifts in this lab are producing [02:03] vaccines that will be shipped around the world [02:25] There are approximately 50, 000 steps at the lab [02:28] it begins with bags of pure mRNA the molecule that tells cells how to make the proteins that [02:33] launch the immune response and a buffer solution that starts the coding process [02:39] it emerges in bulk at the other end of the process as a liquid destined for vials [02:46] most of the machines are named after the engineers that developed the process [02:50] this one is named after Margaret the first patient in the clinical trials to receive the vaccine [02:56] but the beating heart of the lab is this machine a container that uses pressurized ethanol to encase [03:01] the mRNA and special lipid nanoparticles [03:05] those nanoparticles keep the mRNA protected until it [03:08] can jumpstart the immune response in the body's cells [03:38] Speed is essential but inside the lab everyone moves slowly and methodically [03:45] each of the 50,000 steps is logged by one technician confirmed by a second and only then does it actually happen [03:53] it's very important that the quality of the product and all the raw materials is perfect [04:00] here and so no impurities should be present in all raw materials and nothing which we don't [04:06] want to have in our products [04:08] one wrong move has the potential to damage the final product [04:12] if there's any accidental exposure let's say from an ill-timed sneeze [04:17] the entire batch must be thrown out, all eight million doses that's why everyone wears layers [04:23] of protection and they even disinfect their gloved hands repeatedly [04:45] in the lab where we were filming no one had ever told the technicians how many doses were in a batch [04:56] after that they sprayed another application of disinfectant onto their gloves just to be sure [05:13] based on our technology and on the antigen we were using no I wasn't [05:19] I'm very confident in the technology we have [05:22] until now vaccine development has been a slow process [05:26] the BioNtech vaccine uses a new technology based on mRNA it is revolutionizing the way [05:32] vaccines can be produced [06:03] When the COVID-19 pandemic broke out, BioNtech was primarily a cancer vaccine company [06:08] but by using this new mRNA technology it was able [06:11] to quickly pivot to a coronavirus vaccine [06:15] when you look back at any project you've ever done you've [06:17] always looked back at the start and go wow okay if I'd known that now i could have cut you know a few [06:24] hurdles out of my way earlier right but you're in a situation where you're doing something [06:29] especially for us as a smaller company that was unprecedented [06:32] the second part of the process happens at another factory [06:35] where vials are filled and packed into boxes for shipment [06:38] as the cycle comes to an end there's little time to celebrate after all another batch is waiting to be made ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/6052238/breakthrough-covid-19-infections-vaccinated/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/6052238/breakthrough-covid-19-infections-vaccinated/"},"headline":"Why 'Breakthrough' Infections Even After COVID-19 Vaccinations Shouldn’t Be 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