COVID-19 survey in Baja California, Mexico, in February of 2021

Baja California is a State located in the north-western region of Mexico,
which borders with the United States. This area is of particular
importance in terms of epidemiological surveillance, given that the
busiest port of entry to the U.S. is located in the Tijuana-San Diego
region, which is also one of the busiest ports of entry in the world.
During the first year of the COVID-19 pandemic, Baja California had the
second mortality rate in Mexico due COVID-19. We conducted a
cross-sectional study to know the prevalence of COVID-19 in the general
population at the beginning of 2021, right after the second wave of
COVID-19 cases in the State. We carried out a population-based survey in
the 3 largest cities of Baja California, Mexico: Mexicali, Tijuana, and
Ensenada. The selection of households followed a probabilistic, 3 stage
approach, with a total of 1,126 individuals included, which were
representative of a population of 2.7 million after weighting. Real Time
Polymerase Chain Reaction (RT-qPCR) was used to assess SARS-CoV-2
infection in nasopharyngeal swabs and IgG seroprevalence was evaluated in
finger stick blood samples. We also assessed the level of knowledge,
attitudes, and practices on COVID-19 prevention in the general population.
In general, Baja California had similar COVID-19 prevalence rate compared
to other States in Mexico, and crossing the border with the U.S. was not
associated to higher odds of infection. Ensenada had a higher prevalence
of COVID-19 by RT-qPCR compared to Tijuana and Ensenada. The
level of health literacy on COVID-19 shows important areas of opportunity,
along with a considerable high rate of vaccine hesitancy. Our findings on
this important area in the Mexico-United States border show that the
dynamics of COVID-19 are complex, and prevalence rates can significantly
differ even within the same region. More work needs to be done in terms of
health promotion in the general population of Baja California in order to
achieve better health outcomes in future public health emergencies of
international concern.