About China-US tax treaty

The china-US tax treaty (publication 901, page 14)
says that residents of china doing research in US
do not pay US income tax for three years.

My question is what happens to the Social Security tax
and Medicare tax? Are they also included in the
above statement? Or I can ask back the federal
and state income tax only?

Thanks very much for sharing your understanding and experience.

Happy tax-return filing!