The downturn in a usually vibrant opening day came despite the Trade Development Council offering 35,000 free admission tickets for people who have received at least one dose of a Covid-19 vaccine.
Up to 10,000 such tickets were made available yesterday before noon, with visitors entering for free by just presenting their vaccination records.
For others, this year marked the first time they could pay for admission directly by Octopus.
One visitor, Steven Liu, said that although the anti-epidemic measures made him feel safe, it also meant a longer wait in queues for those providing contact details through registration forms.
Of this year's 763 exhibitors, more than 60 had incentives for the vaccinated, with Spanish Bookstore Hong Kong offering a 10 percent discount.
Sayaka Wong, a representative of the Hong Kong China Tourism Press, said crowd-control measures implemented this year might have made it seem as if there were fewer people compared to 2019 but that the number of people present was "already impressive."
Raymond Lam from Match Media said his booth had not recorded any sales before noon and hoped more people would visit the fair after lunch hour.
Subculture president Jimmy Pang Chi-ming cited fewer mainlanders and low consumption demand for his estimate that sales are expected to drop 20 percent.
He said the publishing sector agreed not to sell books about June 4 and the anti-fugitive amendment bill to avoid being reported to the authorities.
The NHS said the devices used to monitor blood-oxygen levels at home may give inaccurate readings for people with darker skin.