The fast-spreading Delta virus is now dominant in California and at least 4 other states, data indicates

• The highly transmissible Delta coronavirus variant is set to become dominant in the US soon.
• Data from California officials suggests Delta is already dominant there.
• Iowa, Arkansas, Missouri and Utah also published data indicating the variant is dominant.

Data indicates the Delta variant of the coronavirus is already dominant in five US states.

The variant, which is more transmissible than previous ones, has reached all 50 states. It is widely expected to become dominant in the country over the next couple of weeks.

Some states are further along the curve than others. Data suggests it has already taken over in at least five. This includes California, the most populous state.

A variant is considered dominant once it causes a greater proportion of infections than any other. It can reach this level before accounting for 50% of cases, though nations where Delta has existed the longest are registering close to 100% dominance.

California

The Delta variant made up 35.6% of sequenced cases submitted to the international GISAID database during the most recent available period, according to the California Department of Public Health. That was higher than the previously dominant variant, Alpha, which made up 34.3% of cases.

Iowa

In the week of June 21, the Iowa State Hygienic lab sequenced 47 cases of the virus, 53% of which involved the Delta variant, according to KWWL.

Arkansas

Fifty-six percent of sequenced Arkansas cases were due to Delta as of June 24, according to Action 5 news.

Missouri

St. Louis Public Radio cited Dr. George Turabelidze, an epidemiologist at the state Department of Health and Senior Services as saying that of Wednesday the variant made up about half of the cases in Missouri caused by variants.

Utah

Seventy percent, or 334, of the 447 cases sequenced on the week of June 13 involved the Delta variant, according to Utah Department of Health data.

In the graph below, the variants are called by their scientific names. Delta, or B.1.617.2, is orange, while Alpha, or B.1.1.7, is green.

The variant could already be dominant elsewhere

The variant is likely to be dominant in more states. Data reported here is from infections recorded a few weeks ago, a lag caused by the length of time taken to collect and analyze the data.

An analysis from the Financial Times published Saturday suggests the variant could already be dominant in 21 states.

These can be seen in the tweet below:

As Eric Topol, the founder of the Scripps Research Translational Institute, says in this tweet, most states sequence a "very low" proportion of overall cases, making the rate of Delta's spread harder to pin down.

Vaccines work, even with the Delta variant

What is encouraging is that two doses of vaccine are highly protective against developing even mild symptoms after catching the Delta variant. On Sunday, President Joe Biden said during July Fourth celebrations that getting vaccinated was "the most patriotic thing you can do."

Data from the UK - where Delta is almost totally dominant - suggests that both doses of the Pfizer-BioNTech vaccine offer 88% protection and that the Oxford University-AstraZeneca vaccine offers 60% protection from symptomatic disease.

One dose of either is thought to be far less protective against developing mild symptoms of the disease but still quite effective at protecting people from developing a worse version of COVID-19.

The UK data indicates the Oxford-AstraZeneca shot offers 71% efficacy against hospitalization and the Pfizer-BioNTech shot offers 94% protection.

Johnson & Johnson and Moderna have also said their vaccines work well against the Delta variant.