Plasma SIVmac251 viral loads after infection. Sixteen monkeys were classified based on the viral load peak after SIV infection as follow: (A) high, (B) medium, or (C) low. Viral loads were monitored up to 2 years after SIV infection. 7 months after (represented as a space in the X axis) eleven surviving monkeys were vaccinated with ML29 and SIV viral loads were reported up to 7 weeks. * denotes monkeys that died before ML29 vaccination. D) Percentage of variation in SIV viral loads is depicted over the first 3 weeks after ML29 vaccination. Seven of the 8 SIV/ML29 monkeys experienced a drop in SIV (median 20%) during the first week after vaccination, but those titers returned the following week.