The Center for Disease Control and Prevention (CDC) reported that in light of new evidence collected on the delta variant, vaccinated but infected persons can transmit SARS-CoV-2, the virus that causes COVID-19 disease.
The delta variant was first detected in October in India, and since its discovery it has exploded like a powder keg around the world, with more than 112 countries now reporting cases of infection with this strain of the coronavirus.
The CDC’s recommendations were based on a joint study with the Massachusetts Department of Health, a state where a massive case of coronavirus infection was observed in Barnstable County, where a group of friends and neighbors gathered to celebrate the 4th of July.
The study detected at least 469 cases of coronavirus infection, 75% of those infected were fully vaccinated. The genomic sequence of 119 out of 133 infected —taken from the sample— had contracted the delta variant.
Although five people were hospitalized in Barnstable, only one of whom was vaccinated, no one died. The CDC also tested the viral load in 127 of the sick, fully vaccinated people and found that their viral load was similar to levels seen in 84 people in the study who were not vaccinated and were also infected with the delta variant.
The suggestion that the vaccinated group could just as easily transmit the virus as unvaccinated people prompted the CDC to reissue the recommendation to wear masks in enclosed spaces.
“High viral loads suggest an increased risk of transmission and raised concern that, unlike with other variants, vaccinated people infected with Delta can transmit the virus,” commented Rochelle Walensky, director of the CDC, who further explained that “the finding is concerning and was a pivotal discovery leading to the CDC’s updated mask recommendation.”
The risk of the delta variant as observed by the CDC
The delta variant is currently responsible for up to 70% of new infections in the United States. The latest data released by the CDC shows infection rates climbing back up to 66,000 infected per day, up from just 13,000 in June.
To date, the delta variant has been shown to be not only more contagious than previous strains of the coronavirus, but also more infectious than diseases such as chickenpox, which used to infect around 4 million Americans a year; however, thanks to vaccination, 93% of infections have disappeared.
The time of exposure to the virus after contact with an infected person is also much shorter; while a PCR test to detect infection requires that exposure to the virus occurred at least seven days in advance in the case of an ordinary strain, with the delta variant, PCR only requires 4 days to detect exposure to the virus.
The Israeli Ministry of Health in a recent statement indicated that although the effectiveness of vaccines to prevent infection has dropped to 67% with the delta variant, most of those infected have mild symptoms or are asymptomatic.
In response to the CDC recommendations, several companies and public entities have again required the use of masks in enclosed spaces to prevent new coronavirus infections within their facilities.
A virologist’s response to CDC recommendations
Given the controversy with the delta variant, virologist Angela Rasmussen, Ph.D., explained that it is very unlikely that COVID-19 will mutate into another variant that can easily evade vaccines.
According to Dr. Rasmussen, there are several reasons why new variants are unlikely to escape the effectiveness of vaccines, “the immune system is more complex than just neutralizing antibodies. A few mutations in the N-terminal domain (NTD) or receptor-binding domain (RBD) of spike are insufficient to escape the totality of the immune response,” said Rasmussen.
“Despite alarmist coverage about ‘breakthrough infections,’ the vaccines were actually evaluated with symptomatic COVID-19 as the primary endpoint, not infection.,” Rasmussen explains; that is, the main reason the vaccines exist is to prevent severe disease, not infection.
Dr. Rasmussen insisted that the priority for public health systems is to get all people vaccinated as soon as possible, not to generate panic: “Full vaccination creates a barrier to replication that is largely insurmountable for the virus. Partial vaccination, on the other hand, may not be. That’s why the one-shot mRNA regimes are a bad idea (and delayed dose strategies in the UK and here in Canada have borne that out).” explains Dr. Rasmussen.
Vaccines continue to be effective in preventing COVID-19
It is important to clarify that transmissibility is not synonymous with mortality and that vaccines retain all their effectiveness in preventing fatal infections, as the CDC itself has said on other occasions.
The CDC’s own web portal clarifies that the probability of dying is practically zero (0.0008 %) and less than 0.0004 % of the population that has been infected while vaccinated has presented serious symptoms. In other words, out of 163 million vaccinated Americans, only 6,239 have been seriously affected by COVID-19.
It is also important to note that the rise in infections is occurring in a context where restrictions have been lifted and most Americans have resumed their mobility and travel throughout the country, without this having led to the peaks experienced during June when quarantines were in place, yet hospital beds remained full.
Although the United States is facing a variant of the coronavirus that is more contagious than previous ones, vaccines have so far proven effective in preventing deaths and serious infections.