#15,967
In mid-April the CDC began reporting on vaccine breakthrough cases - instances when a fully vaccinated individual tests positive for the virus (see CDC: COVID-19 Breakthrough Case Investigations and Reporting) - as reported by local health departments.
While all indications are the current vaccines are highly effective, none are 100% protective against infection, and so a certain number of breakthrough infections are to be expected.
With more than 121 million fully vaccinated Americans, even assuming a 90% effectiveness, 12 million would still be at risk of infection. Those who are older, or are immunocompromised in some way, are expected to be less protected than the general public.
The first three reports issued by the CDC (see here, here, and here) reported on all breakthrough cases - including asymptomatic, hospitalized, and non-hospitalized. The last report (April 30th - below) consisted roughly of 90% mild or asymptomatic non-hospitalized cases.
*241 (29%) of the 835 hospitalizations were reported as asymptomatic or not related to COVID-19.†20 (15%) of the 132 fatal cases were reported as asymptomatic or not related to COVID-19.
Two weeks ago the CDC announced they would be changing their format to only tracking hospitalized or fatal cases - and that they would be skipping the May 7th update - in order to prepare for this new format.
Tracking all cases is admittedly unwieldy, and was never going to capture more than a small percentage of mild or asymptomatic cases - but the optics of this abrupt change have evoked criticism in some circles - as it dilutes and minimizes the number of cases reported by roughly 90%.
After a two week hiatus, the new report of fatal or hospitalized vaccine breakthrough cases was published late Friday (below), and as you'll see the number of cases being reported has been greatly reduced.
Despite the awkward transition, I understand why the CDC would want to focus on more serious hospitalized and/or fatal cases, which are presumably also more accurately tracked and reported than asymptomatic or mild cases.
As we've seen many times in the past, surveillance - at best - can show us trends. All numbers - regardless of the location or the disease - are only subsets of what is really out there.
But, the public really needs to understand the numbers being reported likely only represent a very tiny subset of vaccine breakthrough cases across the nation.
You'll find excerpts from the CDC's updated surveillance page below.
COVID-19 Vaccine Breakthrough Case Investigation and Reporting
This page provides information and resources to help public health departments and laboratories investigate and report COVID-19 vaccine breakthrough cases.
- Vaccine breakthrough cases are expected. COVID-19 vaccines are effective and are a critical tool to bring the pandemic under control. However, no vaccines are 100% effective at preventing illness in vaccinated people. There will be a small percentage of fully vaccinated people who still get sick, are hospitalized, or die from COVID-19.
- More than 115 million people in the United States have been fully vaccinated as of May 10, 2021. Like with other vaccines, vaccine breakthrough cases will occur, even though the vaccines are working as expected. Asymptomatic infections among vaccinated people will also occur.
- There is some evidence that vaccination may make illness less severe for those who are vaccinated and still get sick.
- Current data suggest that COVID-19 vaccines authorized for use in the United States offer protection against most SARS-CoV-2 variants currently circulating in the United States. However, variants will cause some vaccine breakthrough cases.
What CDC is doingCDC is leading multiple vaccine effectiveness studies to ensure COVID-19 vaccines are working as expected. In addition, CDC is coordinating with state and local health departments to investigate SARS-CoV-2 infectionspdf among people who received COVID-19 vaccine (called “vaccine breakthrough cases”) and identify patterns or trends in:
- Patients’ characteristics, such as age or underlying medical conditions
- The specific vaccine that patients received
- Whether a specific SARS-CoV-2 variant caused the infections
- Defining a vaccine breakthrough infection
- For the purpose of this surveillance, a vaccine breakthrough infection is defined as the detection of SARS-COV-2 RNA or antigen in a respiratory specimen collected from a person ≥14 days after they have completed all recommended doses of a U.S. Food and Drug Administration (FDA)-authorized COVID-19 vaccine.
Identifying and investigating hospitalized or fatal vaccine breakthrough cases
As of May 1, 2021, CDC transitioned from monitoring all reported vaccine breakthrough cases to focus on identifying and investigating only hospitalized or fatal cases due to any cause. This shift will help maximize the quality of the data collected on cases of greatest clinical and public health importance.Previous case counts, which were last updated on April 26, 2021, are available for reference only and will not be updated moving forward.
State health departments report vaccine breakthrough cases to CDC. CDC now monitors reported hospitalized or fatal vaccine breakthrough cases for clustering by patient demographics, geographic location, time since vaccination, vaccine type, and SARS-CoV-2 lineage. Reported data include hospitalized or fatal breakthrough cases due to any cause, including causes not related to COVID-19.
To the fullest extent possible, respiratory specimens that test positive for SARS-CoV-2 RNA are collected for genomic sequencing to identify the virus lineage that caused the infection.Some health departments may continue to report all vaccine breakthrough cases to the national database and can continue to submit specimens to CDC for sequencing. However, CDC will focus its monitoring on reported hospitalized and fatal cases.
Developing a data access and management system for reporting COVID-19 vaccine breakthrough cases
CDC developed a national COVID-19 vaccine breakthrough REDCap database where designated state health department investigators can enter, store, and manage data for cases in their jurisdiction. State health departments have full access to data for cases reported from their jurisdiction.
Ultimately, CDC will use the National Notifiable Diseases Surveillance System (NNDSS) to identify vaccine breakthrough cases. Once CDC has confirmed that a state can report vaccination history data to NNDSS, CDC will identify vaccine breakthrough cases through that system. At that time, the state health departments can stop reporting cases directly into the REDCap database. After this change, CDC will upload the available data reported to NNDSS into REDCap database for further review and confirmation by the state health department.
