Increasing SARS-CoV2 cases, hospitalizations, and deaths among the vaccinated populations during the Omicron (B.1.1.529) variant surge in UK
Authors: Emani Venkata R. , Pallipuram Vivek K. , Goswami Kartik K. , Maddula Kailash R. , Reddy Raghunath , Nakka Abirath S. , Panga Sravya , Reddy Nikhila K. , Reddy Nidhi K. , Nandanoor Dheeraj , Goswami Sanjeev 
Published: June 2022

BACKGROUND

There 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.

METHODS

In 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).

RESULTS

Of 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.

CONCLUSIONS

There 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.