The protest began about 40 minutes after Yusuf resumed at the headquarters of the agency in Abuja.
The unionists who sang protest songs said the reinstatement of Yusuf would thwart his investigation by the Economic and Financial Crimes Commission.
The protesters, who described the reinstatament saga as ‘Yusufgate’, said it was a mockery of President Muhammadu Buhari’s anti-corruption war.
Addressing journalists on the premises of the agency, the Chairman of the NHIS arm of the union, Mr. Razaq Omomeji, said the protests would continue until Buhari reversed Yusuf’s reinstatement.
Omomeji said Yusuf had bastardised the scheme and his return would only worsen affairs at the agency.