A small number of Californians who were fully vaccinated against COVID-19 later tested positive for the virus.
These so-called ‘breakthrough’ cases occur when people contract the disease 14 days or more after receiving their second dose of the Pfizer-BioNTech or Moderna vaccine or the one-shot Johnson & Johnson jab, and which officials say are not surprising.
Out of 19.5 million people in California who completer their vaccine series, just 7,553 have gotten sick with the virus – meaning a breakthrough case rate of 0.039 percent.
Among those 7,553 people, most had mild COVID-19 cases. Only 62 died from the virus.
While these numbers reinforce how well the vaccines work, limited reporting on breakthrough cases leaves scientists with questions such as which variants are more likely to cause those breakthroughs.
Out of almost 20 million Californians who are fully vaccinated against COVID-19, under 8,000 have later gotten the disease. Pictured: A teenager receives her first shot at a Los Angeles high school, 13,May
The Covid vaccines currently in use in the U.S. – Pfizer-BioNTech, Moderna, and Johnson & Johnson – are all extremely good at protecting people against the coronavirus.
These vaccines have lived up to their promise from clinical trials, allowing millions of Americans to go mask-free, travel, and otherwise return to normal life.
Still, in rare cases, people do get infected with the coronavirus after completing a vaccine regimen.
These rare cases are called breakthrough cases. Scientists track these breakthroughs as a way to continuously examine how well the vaccines work.
Recent data from California adds more evidence to that trend.
As of June 30, the state has reported 7,553 breakthrough cases out of 19.5 California residents who are fully vaccinated.
That amounts to one breakthrough case for every 2,583 vaccinated people, or a breakthrough case rate of 0.039 percent.
‘The way we should think about these cases is that they’re very rare,’ Dr George Rutherford, an epidemiologist at the University of California, told CalMatters.
Out of those 7,553 cases, 584 fully vaccinated Californians went to the hospital with a COVID-19 infection.
The California Department of Public Health notes, however, that many of those people could have been hospitalized for reasons unrelated to Covid but were tested for Covid upon admission.
Data on hospitalization are also missing for about half of California’s breakthrough cases.
Only 62 of those Californians with breakthrough cases died with Covid. But again, some of those deaths may have been from other primary causes.
Only 62 Californians have died from Covid after being fully vaccinated. Pictured: A sign advertises a vaccination site in Union Station, Los Angeles, on June 10
Nationwide, fewer than 5,000 people have been hospitalized with or died from Covid after being fully vaccinated.
The Centers for Disease Control and Prevention (CDC) report 4,427 breakthrough hospitalizations and 879 deaths, as of June 28.
Between January 1 and April 30, the CDC reported 10,262 breakthrough cases – at a time when over 100 million Americans had been fully vaccinated.
Starting in May, however, the agency has only investigated and reported those breakthrough cases that lead to hospitalization and death.
The CDC made this decision in order to focus on investigating more severe breakthrough cases, as opposed to those that result in mild symptoms or no symptoms.
But some experts have said it is still important to track mild breakthrough cases, in order to look for trends – and determine whether any new variants are causing the breakthroughs.
‘Ferreting [breakthrough cases] out will help researchers confirm the effectiveness of COVID-19 vaccines, detect coronavirus variants that could evade our immune defenses, and estimate when we might need our next round of shots—if we do at all,’ Katherine J. Wu wrote in The Atlantic in May.
Most state public health agencies have followed the CDC’s lead and are not tracking breakthrough cases, according to a recent analysis by the Rockefeller Foundation.
California’s public health agency is tracking breakthroughs in its state by matching positive test records with vaccination records.
The state has not released sequencing information on its cases, however. It’s unknown how many of those 7,553 people may have been infected with the Indian ‘Delta’ variant.
Studies thus far have shown that the Pfizer, Moderna, and Johnson & Johnson vaccines all work well against the Delta variant.
But without more information on the variants behind breakthrough cases – and with the Delta variant spreading rapidly across the U.S. – it is difficult for scientists to closely monitor the situation.