Study: Annual COVID-19 vaccine campaign with second dose reduces disease burden, costs

Key takeaways:

• The campaign reduced direct health care costs by over $3 billion over a single year.
• The optimal time interval between doses was 5 months, with a possible range of 3 to 6 months.

An annual COVID-19 vaccination campaign, in which second doses were administered to certain at-risk populations, was associated with reduced disease burden and health care costs, a study showed.

Chad R. Wells, PhD, a postdoctoral research associate at Yale School of Public Health, and colleagues, noted that the FDA has proposed an annual, single-dose vaccination against SARS-CoV-2 infection for most people, like influenza vaccination, “with a potential second dose for those at risk for severe outcomes, including children [aged] younger than 2 years and adults aged 50 years or older.”

“A synchronized pattern between the two diseases suggests that, as with influenza, vaccination campaigns against SARS-CoV-2 before an anticipated surge would reduce the disease burden,” they wrote in the Annals of Internal Medicine. “However, the effectiveness of this strategy remains undetermined, with unknown timing of a surge and the possibility of semiannual COVID-19 epidemics.”

In the study, Wells and colleagues developed an age-structured dynamic model of infectious disease transmission that used contact patterns to simulate COVID-19 incidence, hospitalizations and costs under various vaccination strategies. The primary simulation included the FDA-proposed annual vaccination campaign with a second dose for young children and adults over the age of 50 years. The researchers also assessed alternative scenarios where a second dose was assigned to one of three age groups: those aged 18 to 49 years, those aged 50 to 64 years or those aged 65 years and older.

In the models, the researchers assumed that uptake of the COVID-19 vaccine would be similar to that of influenza vaccination.

They found that in comparison to a single-dose campaign, a second booster resulted in:

• 123,869 fewer hospitalizations (95% UI, 121,994-125,742); and
• 5,524 fewer deaths (95% UI, 5,434-5,613).

Ultimately, the campaign saved $3.63 billion in direct health care costs over a year in the researchers’ model.

The optimal interval between doses among adults aged 50 years and older and in children aged younger than 2 years was around 5 months, with a potential range of 3 to 6 months.

“This timing is projected to have the largest effect on reducing direct health care costs,” Wells and colleagues noted.

The researchers added that among alternative vaccination strategies, prioritizing adults aged 18 to 49 years or 50 to 64 years was more effective at reducing costs compared with prioritizing only those aged 65 years and older “because of differences in population-level vaccine immunity, extent of direct protection, and contact mixing across age-stratified groups.”

They suggested that if at-risk populations are reluctant to receive a second dose, then offering a second dose to those aged 18 to 49 years could provide indirect protection for older adults.

The researchers concluded that monitoring both the seasonal and evolutionary patterns of COVID-19 “is critically important to inform decisions on vaccination strategies and the development of new vaccines to maintain population immunity.”