Sweden's Public Health Agency reported earlier that of the 130 COVID-19 deaths between September 1-24, 70 percent are fully vaccinated.
Possible reasons for the increase in deaths include the diminishing effectiveness of the vaccine over time, the easing of restrictions and the surge of the delta strain.
Sweden's cases numbers fell after health officials scaled back restrictions at the beginning of June, with no fatalities reported in the country throughout July and August. However, deaths began to climb by mid-September, when nearly 75 percent of Swedes older than 16 were fully vaccinated.
The recent surge in infections also led to the highest number of cases in senior care residents since February.
However, a new testing protocol announced by Swedish authorities may make breakthrough cases less of a factor in future reporting. Just days after the agency reported the spike in post-vaccination deaths, Sweden's health agency announced that fully vaccinated individuals with symptoms will be exempt from testing requirements.
In the U.K., similar breakthrough surges were observed. A report by the UK Health Security Agency (UKHSA) noted that most British COVID-19 deaths were also among the fully vaccinated, as were the hospitalizations.
Between September 6 and October 3, 70 percent of deadly COVID cases occurred in fully vaccinated individuals. There were 2,281 deaths in vaccinated individuals compared to the 611 in unvaccinated within 28 days of a positive test.
The COVID-19 fatalities among the fully vaccinated have shown a dramatic increase since August. Reports showed that there had been 600 COVID-19 deaths in the unvaccinated population between August 9 and September 5, while 1, 659 deaths were recorded in the fully vaccinated ones.
The latest figures also showed that vaccinated patients made up most of the COVID-19 hospitalization. There were 3,910 vaccinated patients admitted between September 6 and October 3 compared to 2,400 unvaccinated patients.
The rise in breakthrough cases in the U.K. reflects trends in other highly-vaccinated countries, including the United States. A presentation from the Department of Defense found that about 60 percent of elderly Medicare patients hospitalized for COVID-19 before August 7 were "fully vaccinated."
Vermont reported that fully vaccinated individuals account for 76 percent of deaths from the coronavirus, while Maryland reported that more than 40 percent of recent virus-related deaths in the state came from fully vaccinated patients.
Public data also showed that many other countries are now struggling with COVID-19 breakthrough cases, including Australia where 36 of 49 nursing home residents who died from the virus were fully vaccinated. (Related: How CDC manipulated data to create 'pandemic of the unvaxxed' narrative.)
The first Black U.S. secretary of state, Colin Powell, recently died from COVID-19 complications despite being fully vaccinated. Around 7,000 Americans also met the same fate. However, doctors still say that death in fully vaccinated individuals remains rare as they continue to push people to get the COVID-19 vaccine.
Breakthrough cases happen for different reasons in individuals, said infectious disease specialist and medical microbiologist Don Vinh. The delta variant is more infectious than previous variants of the virus, and it can account for some of the deaths. Immunity after vaccination may also wane over time. And some people's immune systems are simply not strong enough.
"There are a group of people who have either conditions or treatments for their conditions that compromised their immune system and prevent them from being able to even adequately respond to the vaccine to begin with," said Vinh, who works at McGill University Health Centre.
Elderly individuals, for instance, may have weaker reactions to the vaccine. Rod Russell, a professor of virology and immunology at Memorial University, said that older individuals are a cause of concern. "We recognize now that antibody levels do decline. And then in older people, there’s a chance that they may not be able to fight infection if they get it."
According to data from the Centers for Disease Control and Prevention, 85 percent of fully vaccinated Americans who died from COVID-19 were 65 or older.
Read more at Pandemic.news.