The duration of symptoms is shorter in vaccinated persons who become infected with the Omicron variant compared to the delta variant. The symptoms are also milder, according to a study from the UK published in The Lancet.¹

In this study, data from 63,002 Covid-positive patients between June 1, 2021 and January 17, 2022 was analysed. These patients, aged 16 - 99 years, had reported their symptoms in the ZOE COVID app. The enrolled subjects had taken at least two doses of a Covid-19 vaccine and their BMI ranged from 15 kg/m2 to 55 kg/m2. Patients from the delta (June 1 to Nov 27, 2021) and Omicron (Dec 20, 2021, to Jan 17, 2022) waves were matched for age, sex and vaccination dose.

It was found that loss of smell was reported more often during the delta wave than in the omicron wave; 52.7% vs 16.7%, respectively. Sore throat occurred more frequently during the omicron wave (70.5%) compared to the delta wave (60.8%). Hoarse voice was 1.2 times more likely to occur with Omicron infection than with delta infection. Hospitalizations within 7 days before or after the positive test were fewer during the omicron wave (1.9%) versus the delta wave (2.6%). Omicron patients recovered within one week of onset of symptoms compared to Covid patients in the delta wave, where symptoms lasted for nearly 9 days with an odds ratio of 2.49. Fully vaccinated and boosted individuals were more likely to experience symptoms for a shorter duration. The three typical symptoms of Covid during the delta wave – fever, persistent cough and loss of smell – occurred less often during the Omicron wave.

This study demonstrates that symptoms of omicron are not similar to those seen with the delta variant. The symptoms are milder than delta and patients, particularly who have also received the third vaccine dose, also recover earlier. Omicron is also less likely to lead to hospitalizations.

Reference

1. Cristina Menni, et al. Symptom prevalence, duration, and risk of hospital admission in individuals infected with SARS-CoV-2 during periods of omicron and delta variant dominance: a prospective observational study from the ZOE COVID Study. Lancet. April 07, 2022. DOI:https://doi.org/10.1016/S0140-6736(22)00327-0