Five Science Points Behind the CDC’s Latest Mask Guidance

Helix’s new study, where the Covid-19 test helped track many variants, shows how quickly it happened. Alpha accounted for 67% of cases in mid-May. After 10 weeks, it dropped to only 2.3% and was replaced by Delta, which is estimated to be about 90% of cases.

“This is one of the most infectious viruses we know. Measles, chickenpox, this is all there,” Warrensky told CNN Thursday.

Early strains of coronavirus resembled a common cold in terms of how fast they spread, according to internal CDC documents. If left unchecked, infected individuals may have infected an average of 2-3 people with the virus early in the outbreak. But now, in Delta, that number can go from 5 to 9.

According to Helix’s preprint study, this may be partially explained by Delta’s ability to “replicate faster and lead to higher viral load earlier in infection compared to other variants.” there is.

The CDC document also states that Delta is “more likely to be serious” than before.

Breakthrough infections can be contagious, but infections are caused by unvaccinated

Prior to Delta Air Lines, even if you had a breakthrough infection, you may have less virus in your respiratory tract. Therefore, if you are vaccinated, you are less likely to infect others.

Vaccination reduces the chances of getting Covid-19 in the first place, experts say, but new data show that Delta is similar for both vaccinated and unvaccinated people. Causes viral load.

“The idea that someone is still positive and can generate enough virus to infect the nose and mouth is what this data actually shows,” said CNN’s Chief Medical Correspondent. Dr. Sanjay Gupta explains.

The discovery that the delta variant resulted in similar viral load was “a crucial finding that led to the CDC’s updated mask recommendations,” Warensky said Friday.

However, viral load itself may not be a definitive measure of infectivity. For example, the immune system of vaccinated people contains several moving parts that can affect the amount that can be spread.

Warrensky said ongoing outbreak investigations would help reveal more about what would happen when these breakthrough infections occur.

“We are currently tracking these clusters to understand the effects of forward infections in these vaccinated people,” she said earlier this week. “But again, we believe that the majority of infections occur through unvaccinated and unvaccinated people.”

Vaccination is the best tool for Delta

The efficacy of the Covid-19 vaccine varies. When moving from asymptomatic infection to hospitalization and death, the ultimate efficacy is over 90%.

According to CDC documents, the vaccine is estimated to triple the risk of infection and reduce the risk of serious illness and death by more than a tenth.

“Vaccination can prevent serious illness, hospitalization and death, even for Delta Air Lines,” Warensky said this week.

CNN’s Gupta noted that he confirmed that this trend was reflected in the Covid-19 figures at the national level.

“When we talk about the increase or surge in cases last year, almost as expected, we’ll see a certain percentage of subsequent hospitalizations and a certain percentage of people dying in the weeks that follow,” he said.

However, the country has not yet seen tandem hospitalizations and deaths of the same magnitude. Experts say this metric is important when discussing when and when people are advised to take booster shots-but for now, vaccines are in this regard. It continues to hold up.

Mask is another necessary tool

More than eight in ten Americans live in counties that have enough Covid-19 infections with the CDC, which is recommended to be masked indoors, even if vaccinated.

This move has led to updates to mask policies in many places, including businesses and school districts.

The CDC’s motivation for updating the guidance was not only the epidemic and infectivity of the delta, but also the lower-than-expected intake of the Covid-19 vaccine.

“Given the higher infection rates and current vaccination rates, universal masking is essential to reduce delta mutant infections,” said the internal CDC document.

However, experts say that you can control the virus by putting a strategy on top of vaccination. In particular, there are measures such as distance and testing as well as masks.

“The steps needed to manage this are extreme. The steps needed are extreme,” Warrensky told CNN.

As more people are vaccinated, we will see more breakthrough infections

Breakthrough infections were always expected. Simply put, no vaccine is 100% effective.

As more people get vaccinated, it makes sense to see more breakthrough infections.

As shown in the CDC document, a mathematical formula known as Bayes’ theorem can give us some rough estimates.

In a population where 60% are fully vaccinated with 80% effective vaccine, nearly a quarter of infections are expected to be a breakthrough.

If you change either number to 70%, nearly one-third of infections can reach a breakthrough.

Of course, this assumes that everyone in the population is the same. A disproportionate number of breakthrough infections may be seen in populations that may be less effective with the vaccine, for example, people with immunodeficiency or living in elderly housing with care.

But when you look at the percentage of vaccine efficacy, it’s talking about the entire population. I’m not saying that individuals are 70%, 80%, or 90% protected.

“The immune system is very complex, involving T cells as well as B cells,” Dr. Monica Gandhi, an infectious disease specialist at the University of California, San Francisco, told CNN by email.

“Antibodies do not give the whole picture of immunity.”