; and (B) engaged in the practice of medicine, provision of healthcare services, or medical research involving the diagnosis, treatment, or prevention of COVID–19 disease. (3) Priority date Subject to paragraph (5), immigrant visas under paragraph (1) shall be made available to aliens in the order in which a petition on behalf of each such alien is filed with the Secretary of Homeland Security, except that an alien shall maintain any priority date that was assigned with respect to an immigrant visa petition or application for labor certification that was previously filed on behalf of such alien. (4) Protections for surviving spouses and children (A) Surviving spouses and children Notwithstanding the death of an alien described in paragraph (2), the Secretary of State may approve an application for an immigrant visa, and the Secretary of Homeland Security may approve an application for adjustment of status to lawful permanent resident, filed by or on behalf of a spouse or child of such alien. (B) Age-out protection For purposes of an application for an immigrant visa or adjustment of status filed by or on behalf of a child of an alien described in paragraph (2), the determination of whether the child satisfies the age requirement under section 101(b)(1) of the Immigration and Nationality Act ( 8 U.S.C. 1101(b)(1) ) shall be made using the age of the child on the date the immigrant visa petition under paragraph (1) was approved. (C) Continuation of nonimmigrant status A spouse or child of an alien described in paragraph (2) shall be considered to have maintained lawful nonimmigrant status until the earlier of the date— (i) on which the Secretary of Homeland Security accepts for filing, an application for adjustment of status based on a petition described in paragraph (1)