A case-case study on the effect of primary and booster immunization with China-produced COVID-19 vaccines on prevention of pneumonia and viral load among vaccinated persons infected by Delta and Omicron variants.

Using a three-prefecture, two-variant COVID-19 outbreak in Henan province in January 2022, we evaluated the associations of primary and booster immunization with China-produced COVID-19 vaccines and COVID-19 pneumonia and SARS-CoV-2 viral load among persons infected by Delta or Omicron variant. We obtained demographic, clinical, vaccination, and multiple Ct values of infections ≥3 years of age. Vaccination status was either primary series ≥180 days prior to infection; primary series <180 days prior to infection, or booster dose recipient. We used logistic regression to determine odds ratios (OR) of Delta and Omicron COVID-19 pneumonia by vaccination status. We analysed minimum Ct values by vaccination status, age, and variant. Of 826 eligible cases, 405 were Delta and 421 were Omicron cases; 48.9% of Delta and 19.0% of Omicron cases had COVID-19 pneumonia. Compared with full primary vaccination ≥180 days before infection, the aOR of pneumonia was 0.48 among those completing primary vaccination <180 days and 0.18 among booster recipients among these Delta infections. Among Omicron infections, the corresponding aOR was 0.34 among those completing primary vaccination <180 days. There were too few (ten) Omicron cases among booster dose recipients to calculate a reliable OR. There were no differences in minimum Ct values by vaccination status among the 356 Delta cases or 70 Omicron cases. COVID-19 pneumonia was less common among Omicron cases than Delta cases. Full primary vaccination reduced pneumonia effectively for 6 months; boosting six months after primary vaccination resulted in further reduction. We recommend accelerating the pace of booster dose administration.

[Surveillance of adverse events following immunization in Henan Province, China between 2010-2011].

OBJECTIVE: To analyze the epidemiological features of adverse events following immunization (AEFI) in Henan Province, China and to evaluate the safety of vaccines currently used in Henan. METHODS: The AEFI cases reported in Henan from January 1, 2010 to December 31, 2011 were collected through the China Surveillance System of Information on National Immunization Program. The descriptive method was used for epidemiological analysis. RESULTS: A total of 2415 cases of AEFI were reported in Henan from January 1, 2010 to December 31, 2011, and 1238 (51.26%) of them were found in Zhengzhou, Luoyang, and Jiaozuo cities. The male-to-female ratio was 1.32:1. Seven hundred and ninety-nine (33.08%) of these cases were less than one year old. Measles vaccine and DPT vaccine (against diphtheria, pertussis, and tetanus) were the main causes of AEFI, contributing to 61.24% of cases; the incidence rates of AEFI among people receiving measles and DPT vaccines were 30.3/105 and 5.0/105, respectively. 1528 cases (63.27%) developed AEFI after the first dose of vaccination. Inflammation and allergic symptoms were the predominant adverse effects caused by the top 5 vaccines AEFI-causing vaccines, and the clinical manifestations were significantly different among AEFI cases caused by different vaccines (χ2=304.5, P<0.001). Among the 2415 AEFI cases, 1946 (80.58%) had common adverse reaction, 348 (14.41%) had rare adverse reaction, 98 (4.06%) had coupling disease, 13 (0.51%) had psychogenic reaction, and 10 (0.41%) had reaction for unknown reasons. The prognosis of most AEFI cases was good, with a cure rate as high as 90.64%. CONCLUSIONS: AEFI occurs mostly in young children and after the first dose of vaccination. This should be brought to the attention of vaccination service personnel and the children's parents.