Knowledge is key to face any disease, but there are few baseline studies from the beginning of the COVID-19 pandemic. The objective was to determine the association between being a vulnerable population and the low knowledge of the population in 17 Peruvian cities at the beginning of the pandemic. Knowledge was measured using a nine-question scale, which asks about the mechanism, symptoms and consequences; this was crosschecked against socio-demographic variables using analytical statistics. Of the 3913 respondents, the lowest knowledge was about how to react to cold symptoms and what treatment a person with an initial non-severe coronavirus infection should follow (37% and 53% correct answers; respectively). In the multivariate analysis, those who had lower percentages of a poor level of knowledge of the disease were those with higher education (aPR: 0.74; 95%CI: 0.62-0.88; p-value=0.001), among those with some postgraduate studies (aPR: 0.59; 95%CI: 0.43-0.68; p-value<0.001), among those who were part of the health personnel (aPR: 0.15; 95%CI: 0.05-0.46; p-value=0.001) and among women (aPR: 0.84; 95%CI: 0.73-0.96; p-value=0.009), on the other hand, the older the age, the worse the level of knowledge of the disease (aPR: 1.012; 95%CI: 1.005-1.018; p-value=0.001), adjusted by 4 variables. There was a low level of knowledge in some aspects and this is associated with some specific characteristics according to being considered a vulnerable population.