Could the delta variant become dominant?
2:01
(CNN) -
All eyes are on the delta variant that is now dominant in the United States as new cases of covid-19 increase week by week and the variant, first identified in India and also known as B.1,617.2, represents a growing share.
But trends in Israel and the UK, where the variant became dominant a few weeks earlier than in the US, offer hope for a less deadly and severe increase than others that have come before.
And experts say that vaccination progress will be the most critical factor in preventing the worst outcomes.
Delta variant moves faster, says expert 2:54
In Israel, the average daily cases are double what they were in mid-April when the first cases of delta were identified in the country.
At that time, there were an average of five deaths per day in Israel.
But despite the rise in the delta variant, which now accounts for more than 90% of new cases in the country, average daily deaths have consistently remained below that.
In fact, Israel has averaged fewer than two COVID-19 deaths per day since the last week of May, according to data from Johns Hopkins University.
The delta variant is a "covid-19 on steroids," according to one expert, as cases rise across much of the US.
In the UK, both cases and deaths are higher than when the delta variant became the dominant strain in the country in mid-May, but cases have risen exponentially faster than deaths.
Average daily deaths in the UK are about twice what they were when the delta variant became dominant, and the cases are about 12 times what they were.
But trends in COVID-19 deaths lag a few weeks behind trends in cases, so the most recent data on deaths should be closer to data on cases from a few weeks earlier.
And even three weeks ago, the average daily case in the UK had multiplied more than the most recent daily deaths.
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While both Israel and the UK presage some optimism about the US delta trajectory, experts say Israel's results have been more overwhelmingly positive due to its substantial vaccination rate.
"In my opinion, vaccines are the most important factor" in the fight against the delta variant, Becky Dutch, a virologist and chair of the department of molecular and cellular biochemistry at the University of Kentucky, told CNN.
When the first cases of the Delta variant were identified in Israel, about 56% of the population was already fully vaccinated, according to Our World in Data.
But in the UK, only 2% of the population was fully vaccinated when the delta variant was first identified there, and it only reached 50% vaccination in the last week.
Pfizer: Why is the third dose important?
2:20
"There is reason to have moderate hope, except that the reason deaths and hospitalizations have not increased so much is that there is a fairly high immunity from vaccines and natural infections in people at higher risk," Justin Lessler, a professor of epidemiology at the University of North Carolina, told CNN.
In a statement released Monday, the Israeli government said its analysis has shown that the Pfizer / BioNTech vaccine provides 64% protection against infections caused by the delta variant, but is 93% effective in preventing serious illness and hospitalizations, compared to May research which reported 97% efficacy.
"If we were to choose a flu vaccine that was as effective as current mRNA vaccines appear to be against delta, we would be celebrating. They are only slightly less good against delta than against the originally circulating strain," Lessler said.
"The concern is the places in the US where there have not been many cases of covid and where vaccination rates among the high-risk population are low."
In general, vaccination rates in the US are somewhere between those in Israel and the UK.
About 16% of the population was fully vaccinated when the first cases of delta were identified in the US, and about 48% are fully vaccinated now that the variant has become dominant.
And vaccination rates vary widely across the country.
Less than a third of people in Alabama are fully vaccinated, compared to about two-thirds of people in Vermont, according to the latest data from the U.S. Centers for Disease Control and Prevention (CDC, for its acronym in English).
Israel sees decline in efficacy of Pfizer vaccine 0:44
"America is a mosaic now," Dutch said.
"It depends on where you live. If you live in a place with high vaccination rates and you are vaccinated, I would not be too worried about you. But if you are located in an area of the country with 35% of the population that is vaccinated and you are not vaccinated, that worries me much more. "
And while there is some evidence that the virus can evade natural immunity from previous infections and slightly decrease the effectiveness of vaccines, experts say these findings are something to watch out for, but not cause for panic.
Instead, Lessler says that the rise and spread of the delta and alpha variants are a "warning that the virus will continue to evolve and will continue, in that evolution, to find ways to bypass existing immunity," but that the hope is that the viruses will continue to evolve. vaccines will "virtually eliminate severe disease" for quite some time.
Delta variant
