Columbia subject headings:
Vaccination--Developing countries.
Vaccination--United States.
Vaccines--Research--Government policy.
Harvard subject headings:
Communicable diseases--Developing countries--Vaccination.
Communicable diseases--United States--Vaccination.
Vaccines--Research--Government policy.
Princeton subject headings:
Communicable diseases--Developing countries--Vaccination.
Communicable diseases--United States--Vaccination.
Vaccines--Research--Government policy.