All indications are that the rate of spread of the Omicron variant will lead to an increase in diagnoses within the next 2-3 months worldwide. But what is not clear, and most importantly, is how much pressure the Omicron strain will put on health systems.
The Professors of the Medical School of the National and Kapodistrian University of Athens Gikas Majorkinis and Thanos Dimopoulos (Rector of EKPA) report that there are three factors that will play a catalytic role:
1) the morbidity-mortality of the strain in the unvaccinated population
2) the effectiveness of the vaccines against the Omicron strain after 2 or 3 doses
3) the severity of the re-infection.
Regarding the morbidity-mortality of Omicron the first early data show a profile of reduced severity of the disease in relation to the Delta strain. Some early reports indicate 30% less severity of the disease. If this is verified, this is a significant reduction in morbidity, without, however, allowing us to safely assume that health systems will not be strained.
Regarding the efficacy of vaccines The important element is the prevention of morbidity-mortality which largely depends on whether the booster dose has been given. Preliminary data show that morbidity-mortality with 2 doses of Pfizer vaccine remains relatively high at 70% for severe disease. In this we should note that the decrease in apparent efficacy may be due in part to the fact that the severity of Omicron in the unvaccinated is lower. The addition of the booster (or third) dose, as several studies have shown, enhances efficacy against mutant strains, as evidenced by laboratory studies in Omicron. According to Anthony Fauci, Director of the US National Institute of Allergy and Infectious Diseases, the booster dose significantly increases protection against Omicron. Specifically, the third dose of BNT162b2 increases antibody levels against the Omicron strain by 25-fold and neutralizing antibody levels by 35-fold. Thus, protection against symptomatic disease can reach 75% with the booster dose. Although we are currently lacking larger studies on the clinical efficacy of the third dose, the rate at which the third dose will be completed in the general population is expected to play a very important role in stopping the Omicron wave.
Finally the severity of re-infection, ie Omicron infection in people who have had the disease in the past, is expected to play a very large role in populations that have had high exposure such as in Brazil (eg in the city of Manaus in the Amazon), but also in South Africa (e.g. in the town of Gauteng). The gravity of the re-infection will also play a special role in Europe, which is in the phase of exiting the Delta wave. Those who have recently had Delta infection (eg within the last 1-2 months) will have relatively good resistance to new Omicron infection, but the highest resistance is expected in those who have been vaccinated and have been ill in the past. In the Brazilian city of Sao Paulo, for example, a vaccination rate of up to 100% is reported in adults. Given that a large percentage of the population had become ill before the vaccination, it is very likely that the Omicron wave will be milder in areas like Sao Paulo.
Summarizing the data so far, the speed of spread of Omicron will be higher than any previous strain, however, estimating the severity in health systems is relatively difficult to estimate as it is a multifactorial system. The speed of delivery of the booster (third) dose emerges as the most decisive factor in the protection of health systems.
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