Starting antiretroviral therapy within hours of birth drastically shrinks the reservoir of HIV virus - an important step in efforts to cure infections - and improves antiviral immune responses in newborns with HIV, shows a two-year study of a unique cohort of ten infants in Botswana. The findings demonstrate that starting treatment earlier in life than current guidelines recommend could substantially improve health outcomes in infants with HIV, who experience irreversible immune damage if left untreated. HIV infections in newborns represent a huge health burden in developing countries; one study estimated that 300 to 500 infants are infected every day in sub-Saharan Africa. Because HIV infection in newborns can lead to rapid and fatal immune deficiency, the World Health Organization recommends that infected newborns receive antiretroviral treatment within weeks of birth. However, adhering to these recommendations can be difficult in low-resource and remote settings. To understand how the timing of antiretroviral therapy affects newborns, Pilar Garcia-Broncano and colleagues studied samples from infants over two years in Botswana, where around 24% of pregnant women are living with HIV. The subjects consisted of ten infected infants who began treatment on average seven hours after birth, ten infected infants who began treatment on average four months after birth, and 54 infants without HIV. The researchers saw that the earliest-treated infants showed a much smaller viral reservoir - the latent pool of the virus that persists throughout life - compared to the second infant group at week 96. Early treatment also granted other benefits to the infants, who showed more functional HIV-specific T cell responses and antiviral responses in the innate immune system. Garcia-Broncano et al. note that follow-up studies of the infant cohort could reveal additional benefits of early antiretroviral treatment that might appear later in life.