But rates of systemic side effects were similar for men and women after receipt of both types of vaccine.
96% of Veterans Administration hospitals require staff vaccination.
The company said a combo vaccine might help bridge gaps in vaccine coverage while simplifying vaccination.
On average, COVID-19 was tied to 2 more days of sick time than influenza.
High-dose flu vaccine contains 4 times as much hemagglutinin as standard-dose flu vaccine.
The risk of influenza was found to be elevated in people who received the vaccine only in the previous season.
The return on investment of up to $4,637 per vaccination course translates to billions of dollars in net monetary benefits to society, the authors say.
Among the 767 adults in the study, 32% said they had no primary care provider.
A literature review found pneumococcal conjugate vaccines were associated with some protection against flu and other viral respiratory tract infections.
The Yamagata flu B lineage hasn't been confirmed since March 2020 and is no longer thought to pose a health threat.
