If COVID-19 becomes a seasonal virus — like three of the four common-cold coronaviruses — an annual COVID vaccine alongside our flu shot may offer all the protection we need.
President Joe Biden, in a September statement, even described the new COVID-19 boosters as a “once-a-year shot.”
But it’s really too soon to know if COVID-19 will become seasonal, says Otto Yang, MD, a professor in the Departments of Medicine and Microbiology, Immunology and Molecular Genetics at the David Geffen School of Medicine at UCLA.
“When a virus comes into the human population, it takes a while before it settles into a pattern,” Dr. Yang says. “When this hit humans, everybody was susceptible and it was easy for the virus to spread, but once a bunch of people have been infected and/or vaccinated, then it’s not as easy for the virus to spread and a seasonal pattern will emerge if it’s seasonal.”
Anthony Fauci, MD, the nation’s top infectious disease official, predicted at a federal health briefing in September that “in the absence of a dramatically different variant, we likely are moving towards a path with a vaccination cadence similar to that of the annual influenza vaccine, with annual updated COVID-19 shots matched to the currently circulating strains for most of the population.”
Will an annual shot be enough?
Vaccine- and infection-induced protection against COVID-19 wanes after about four months, Dr. Yang says. So if the virus settles into a seasonal pattern, annual vaccination may be enough to reduce infection rates and illness severity during the viral season.
The flu virus, for instance, is seasonal, with most cases arising in the fall and winter. Thus, an annual flu shot that offers protection during the most infectious season prevents influenza from being as deadly as it once was, even though immunity from the flu vaccine lasts much less than a year.
The shots introduced in September — which encode the spike protein of the original strain of the virus and the omicron sub-variants BA.4 and BA.5 currently responsible for most infections — were developed according to a similar rationale as the annual flu vaccine. This new booster aims to protect against the circulating strains of COVID-19, just as the flu vaccine is adjusted each year to protect against predicted circulating strains of that virus.
And, like the annual flu vaccine, the new COVID-19 boosters were developed and authorized without clinical trials with human subjects.
The same RNA platform used for the original COVID-19 vaccine was adapted to include RNA from the omicron variant, Dr. Yang says: “This is the normal process with the flu vaccine, which changes every year.” Moreover, the omicron variants are much more similar to the original virus than flu vaccine strains are to each other year to year, he says.
How much is COVID-19 mutating now?
“It’s been a while since we’ve seen a big new variant,” says Dr. Yang, noting omicron sub-variant BA.5 has been dominant for several months.
The virus has evolved to be better at spreading between humans, he says, as evidenced by mutations to the binding receptor domain, which the virus uses to attach to a cell to infect. The latest mutations make that attachment process more efficient against human cells, which reflects that it has adapted to humans after jumping species from an animal host.
“Mutations happen randomly,” Dr. Yang says. “And if a mutation is helpful to a virus, that virus will have an advantage and take over, compared to its peers.”
That’s what omicron sub-variants BA.4 and BA.5 have done.
Ashish Jha, MD, the Biden administration’s COVID-19 coordinator, says that “barring those variant curveballs,” a once-a-year shot should suffice to protect the majority of Americans from serious illness from COVID-19.
How an infectious diseases doctor protects himself against COVID-19
Dr. Yang says he’s fully vaccinated but is eager to get the new shot. He continues to avoid crowded indoor spaces, and when he can’t, he wears an N-95 equivalent mask when inside in public settings, such as when grocery shopping.
“It’s not like I completely avoid indoor spaces or socializing with friends,” he says. “I just try to make sure it’s risk-balanced,” adding that he does see small groups of low-risk friends indoors, for example.
But he opts for socializing outdoors whenever possible, he says.
“I still have not been infected,” Dr. Yang says. “And I would prefer to keep it that way.”
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