Enlarge / A vial containing Moderna COVID-19 booster vaccine at a vaccination center. (credit: Getty | SOPA Images )

The type of COVID-19 booster dose you get later this year could depend on where you live.

Vaccine maker Moderna is working up two omicron-targeting boosters for different countries. If the company's plans pan out, it will mark the first time that COVID-19 vaccines would target different versions of the pandemic coronavirus in different places. Until now, all vaccines, including boosters, have targeted the ancestral strain of SARS-CoV-2, first identified in Wuhan, China.

Both of Moderna's next-gen booster candidates are bivalent vaccines, which target both the ancestral virus and some version of omicron. One booster option targets BA.1—the version of omicron that first burst out of South Africa last November, causing a towering wave of infection in the US in January 2022. That BA.1-based next-gen booster could be available in the EU, UK,  Australia, and elsewhere later this month or early August. Moderna's other booster option targets BA.4/5 and is intended for use in the US. However, it likely won't be ready until early to mid-fall.

Enlarge / Dr. Peter Marks, director of the Center for Biologics Evaluation and Research within the Food and Drug Administration, testifies during a Senate Health, Education, Labor, and Pensions Committee hearing on the federal coronavirus response on Capitol Hill on March 18, 2021, in Washington, DC. (credit: Getty | Pool )

On Thursday, the US Food and Drug Administration advised vaccine makers to reformulate COVID-19 booster shots for this fall. The boosters would target both the original strain of the pandemic coronavirus plus two new omicron subvariants—BA.4 and BA.5—which became the dominant versions of the virus circulating in the United States this week.

The FDA's announcement comes two days after its independent expert advisors voted overwhelmingly in favor of updating boosters to include an omicron component. The vote—19 in favor, two against—was simply in favor of including an omicron component generally. But, in their afternoon-long discussion, experts offered opinions that led to the FDA's more specific guidance.

Specifically, much of the committee expressed support for combination shots—aka bivalent boosters—that would target both the original virus and a version of omicron. There was also broad support for targeting the omicron subvariants BA.4 and BA.5 specifically, rather than earlier subvariants, such as the first, BA.1, which is no longer in circulation.

Enlarge / A COVID-19 testing tent stands in Times Square on April 27, 2022, in New York City. (credit: Getty | Spencer Platt )

Omicron coronavirus subvariants BA.4 and BA.5 are now accounting for an estimated 35 percent of US cases , according to the Centers for Disease Control and Prevention. The subvariants are on a course to reach dominance at a faster clip than the subvariants before them, including the current reigning subvariant, BA.2.12.1, which is now in decline.

The pair—which share the same mutations in their SARS-CoV-2 spike proteins but have differences elsewhere in their genomes—are expected to reach dominance "in a few weeks," Dr. Shishi Luo tells Ars. Luo is the head of infectious diseases at Helix, a California-based population genomics and viral surveillance company that works with the CDC to help track emerging coronavirus variants nationwide.

It's unclear exactly what's ahead in this latest phase of the pandemic. What we know of the two subvariants so far is mixed.

Enlarge / A long COVID patient sits with her daughter in her wheelchair while receiving a saline infusion at her Maryland home on Friday, May 27, 2022. (credit: Getty | The Washington Post )

Among adults vaccinated against COVID-19, the odds of developing long COVID amid the omicron wave were about 20 percent to 50 percent lower than during the delta period, with variability based on age and time since vaccination.

The finding comes from a case-control observational study published this week in The Lancet by researchers at Kings College London. The study found that about 4.5 percent of the omicron breakthrough cases resulted in long COVID, while 10.8 percent of delta breakthrough cases resulted in the long-term condition.

While the news may seem a little reassuring to those nursing a breakthrough omicron infection, it's cold comfort for public health overall since the omicron coronavirus variant is much more transmissible than delta.

Enlarge / A vial of the current Moderna COVID-19 vaccine. (credit: Getty | Ivan Romano )

A combination COVID-19 booster dose that targets the ancestral strain of SARS-CoV-2 and the initial omicron variant, BA.1, appears to outperform the current booster against both of those versions of the virus, Moderna reported Wednesday .

Specifically, Moderna says the combination booster increased neutralizing antibodies against omicron 8-fold, while the original booster only increased antibody levels around 4.4-fold.

The vaccine maker is angling to have this bivalent shot—dubbed mRNA-1273.214—be the go-to booster for seasonal shots this fall. The company will be submitting its data to the Food and Drug Administration in the coming weeks and says it hopes to have the bivalent booster available by late summer, if not early fall.

Enlarge (credit: Getty | Xinhua News Agency )

Despite early suggestions that the omicron coronavirus subvariant BA.1 would be mild, a massive wave of infections in January caused spikes in hospitalizations and more excess deaths than earlier variants. And subsequent omicron subvariants don't appear to be easing up.

According to a preprint study involving data from more than 1.5 million people in the United Kingdom, an infection with the omicron subvariant BA.2 was more likely to be symptomatic, more likely to cause a larger number of symptoms, and more likely to cause symptoms that people said affected their daily lives "a lot," compared to an infection with BA.1.

In fact, BA.2 wasn't just worse than BA.1; it was bad overall. The study authors analyzed symptom reports linked to infections of the ancestral coronavirus strain and variants alpha, delta, omicron BA.1, and omicron BA.2. The authors found that BA.2 infections were the most likely to cause symptoms compared with all the other variants. And the finding held up when the authors adjusted for time since a booster dose in people who were triple vaccinated, suggesting that waning vaccine protection could not explain the increase in symptom reporting.

Enlarge / Dr. Peter Marks, Director of the Center for Biologics Evaluation and Research within the Food and Drug Administration, testifies during a Senate Health, Education, Labor and Pensions Committee hearing on the federal coronavirus response on Capitol Hill on March 18, 2021 in Washington, DC. (credit: Getty | Pool )

The pandemic coronavirus will likely become a seasonal respiratory virus, much like influenza, requiring annual booster shots each fall, according to three top officials at the US Food and Drug Administration.

In a commentary piece published this week in the medical journal JAMA, the officials make a case for seasonal shots and caution that preparation for this winter's potential surge needs to begin no later than next month.

"The timeframe to determine the composition of the COVID-19 vaccine for the 2022-2023 season, to use alongside the seasonal influenza vaccine for administration in the Northern Hemisphere beginning in about October, is compressed because of the time required for manufacturing the necessary doses," the officials write. "A decision on composition will need to be made in the US by June 2022."