Re: “High-Altitude Environment and COVID-19: SARS-CoV-2 Seropositivity in the Highest City in the World,” by Champigneulle et al.

We read with interest the article by Champigneulle et al. who observed high COVID-19 seropositivity in La Rinconada (Peru), the highest city in the world (Champigneulle et al. 2021). These results suggest dissemination of COVID-19 even at high altitudes. However, some authors have reported that COVID-19 mortality is lower in high-altitude populations (Quevedo-Ramirez et al., 2020; Thomson et al., 2021). As the evolution of the pandemic progresses, we noticed that there has been an increase in research on the relationship between high altitude and COVID-19 mortality in Peru and other countries with people living at high altitude. The objective of this communication was to analyze published studies on this relationship in Peruvian inhabitants.

We performed a bibliographic search in PubMed of articles published from March 2020 to August 2021. The search terms were (COVID-19 OR SARS-CoV-2) AND (Peru*) AND (Altitude*). We included publications that evaluated the relationship between altitude and COVID-19 mortality. There was no restriction by language. Review and opinion articles were excluded. Later, we reviewed the articles' methodology, results, and conclusions.

We found 10 articles that met the established criteria. Of these, 8 (80%) used “Open COVID-19 database” a database maintained by the Ministry of Health of Peru (MINSA). In addition, seven studies (70%) concluded that COVID-19 mortality is lower in cities located at high altitudes as presented in Table 1.

MINSA's database has been used in most studies. However, this database has serious errors and shortcomings. In the first months of the pandemic, several epidemiologists and media reported that the national database did not fit well with local information of various cities. In addition, the Peruvian government reported that this database just registered 37.6% of the total deaths from COVID-19 until May 2021 (Gobierno del Perú, 2021a). Likewise, the departments of Puno and Cusco, both located at high altitudes, had the highest under-registration of deaths. This predominantly high-altitude underreporting could have led to the erroneous conclusion that there is a lower mortality from COVID-19 in Peruvian high-altitude regions.

Some of the studies analyzed did not adjust their findings for other variables that could confound the relationship between mortality and altitude (see Pun et al., 2020 for review). A more accurate and robust analysis should incorporate into the statistical models, variables at individual and population levels. At the individual level, variables such as age, gender, and comorbidities should be used for adjusting mortality, as they are well-known factors related to mortality in COVID-19.

Given that inequities in health access are described in high-altitude populations (Sánchez-Moreno, 2013), characteristics of the health system such as the number of health professionals, hospital occupation rates, and number of mechanical ventilators should be also adjusted in the analysis. Nowadays, another important factor to consider when studying COVID-19 mortality is immunization rates. This is especially important because Puno, a high-altitude Peruvian region, has the lowest vaccination rate in the whole country (19.3%) (Gobierno del Perú, 2021b).

In conclusion, to conclude with the current data that high-altitude inhabitants have protection against COVID-19 mortality will generate errors in decision-making policies and resource allocations, as well as give a false sense of security to this population.