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BACKGROUNDThere were increased SARS-CoV2 hospitalizations and deaths noted during Omicron (B.1.1.529) variant surge in the UK despite decreased cases, and the reasons are unclear. METHODSIn this retrospective observational study, we analyzed reported SARS-CoV2 cases, hospitalizations, and deaths during the COVID-19 pandemic in the UK. We also analyzed variables that affect the outcomes (including ethnicity, deprivation score, vaccination disparities, and pre-existing conditions). We also analyzed the vaccine effectiveness among those [≥]18 years of age (from August 16, 2021 to March 27, 2022). RESULTSOf the total cases (n= 22,072,550), hospitalizations (n=848,911), and deaths (n=175,070) due to COVID-19 in the UK; 51.3% of cases (n=11,315,793), 28.8% of hospitalizations (n=244,708), and 16.4% of deaths (n=28,659) occurred during the Omicron variant surge as of May 1, 2022. During the latter part of the Omicron variant surge (February 28 - May 1, 2022 period), we observed a significant increase in the proportion of cases (23.7% vs 40.3%; RR1.70 [1.70-1.71]; p<0.001) and hospitalizations (39.3% vs 50.3%; RR1.28 [1.27-1.30]; p<0.001) among [≥]50 years of age, and deaths (67.89% vs 80.07%; RR1.18 [1.16-1.20]; p<0.001) among [≥]75 years of age compared to the earlier period (December 6, 2021-February 27, 2022) during the Omicron variant surge. Using the available data from vaccine surveillance reports, we compared the Omicron variant surge (December 27, 2021-March 20, 2022) with the Delta variant surge (August 16-December 5, 2021). Our comparative analysis shows a significant decline in case fatality rate (all ages [0.21% vs 0.39%; RR 0.54 (0.52-0.55); p<0.001], over 18 years of age [0.25% vs 0.58%; RR 0.44 (0.43-0.45); p<0.001], and over 50 years of age [0.72% vs 1.57%; RR 0.46 (0.45-0.47); P<0.001]) and the risk of hospitalizations (all ages [0.62% vs 0.99%; RR 0.63 (0.62-0.64); p<0.001], over 18 years of age [0.67% vs 1.38%; RR 0.484 (0.476-0.492); p<0.001], and over 50 years of age [1.45% vs 2.81%; RR 0.52 (0.51-0.53); p<0.001]). Both the unvaccinated (0.41% vs 0.77%; RR 0.54 (0.51-0.57); p<0.001) and vaccinated (0.25% vs 0.59%; RR 0.43 (0.42-0.44); p<0.001) populations of over 18 years of age showed a significant decline in the case fatality rate during the Omicron variant surge when compared to the Delta variant surge. In summary, a significant decline in the risk of hospitalizations was observed both among the unvaccinated (1.27% vs 2.92%; RR 0.44 (0.42-0.45); p<0.001) and vaccinated (0.65% vs 1.19%; RR 0.54 (0.53-0.55); p<0.001) populations of over 18 years of age during the same period. We observed negative vaccine effectiveness (VE) for the third dose since December 20, 2021, with a significantly increased proportion of SARS-CoV2 cases hospitalizations, and deaths among the vaccinated; and a decreased proportion of cases, hospitalizations, and deaths among the unvaccinated. The pre-existing conditions were present in 95.6% of all COVID-19 deaths. We also observed various ethnicity, deprivation score, and vaccination rate disparities that can adversely affect hospitalizations and deaths among the compared groups based on vaccination status. CONCLUSIONSThere is no discernable optimal vaccine effectiveness among [≥]18 years of age and vaccinated third dose population since the beginning (December 20, 2021) of the Omicron variant surge. Other data including pre-existing conditions, ethnicity, deprivation score, and vaccination rate disparities need to be adjusted by developing validated models for evaluating VE against hospitalizations and deaths. Both the vaccinated and unvaccinated populations showed favorable outcomes with a significant decline in case fatality rate and risk of hospitalizations during the Omicron variant surge. The suboptimal vaccine effectiveness with an increased proportion of cases among the vaccinated population was associated with a significantly increased proportion of hospitalizations and deaths during the Omicron variant surge. This underscores the need to prevent infections, especially in the elderly vaccinated population irrespective of vaccination status by employing uniform screening protocols and protective measures.
RESUMO
BackgroundTo assess the comprehensive dynamics of outcomes during the SARS-CoV2 B.1.617.2 (Delta variant) compared to the Alpha variant outbreak in the United Kingdom. MethodsIn this observational study of the cases reported by Public Health England for confirmed (sequencing and genotyping), SARS-CoV2 cases Delta variant (n=592,692) and Alpha variant (n=150,934) were used. Outcomes were analyzed by age groups and compared with all reported weekly cases in the UK. ResultsThe Delta variant surge is associated with a significantly lower case fatality rate (0.43% vs 1.07; RR 0.39; 95% CI 0.37-0.42; P<0.0001); lower odds of hospitalization (2.1% vs 3.0%; RR 0.70; 95% CI 0.68-0.73; P<0.0001) than the Alpha variant. During the Delta variant surge there were significant increased cases (11.3% to 21.1%, RR 1.87; 95% CI 1.84-1.89; P<0.0001), hospitalizations (40.2% to 56.5%; RR 1.40, 95% CI 1.3-1.46; P<0.0001) among confirmed Delta variant cases in the [≥]50 years age group during the August 3-September 12, 2021 period compared to earlier reported cases. There was also a significant increase in total weekly COVID-19 deaths noted among [≥]70 years old age group (71.4% to 75.1%; RR 1.05; 95% CI 1.01-1.08; P=0.0028) during August 6-October 8, 2021 compared to June 4-July 30, 2021 period. ConclusionsThe Delta variant surge is associated with significantly lower mortality and hospitalizations than the Alpha variant. As the Delta variant surge progressed, [≥]50 years old had a significant increased percentage of cases, hospitalizations and a significant increased COVID-19 deaths occurred among [≥]70 years old age group.
