Vaccines Against COVID-19: A Review

SARS-CoV-2 Vaccine Effectiveness in Hospitalized Patients: A Multicenter Test-Negative Case-Control Study

BACKGROUND

Phase III clinical trials have documented the efficacy of the SARS-CoV-2 vaccines in preventing symptomatic COVID-19. Nonetheless, it is imperative to continue analyzing the clinical response to different vaccines in real-life studies. Our objective was to evaluate the effectiveness of five different vaccines in hospitalized patients with COVID-19 during the third COVID-19 outbreak in Mexico dominated by the Delta variant.

METHODS

A test-negative case-control study was performed in nine tertiary-care hospitals for COVID-19. We estimated odds ratios (OR) adjusted by variables related a priori with the likelihood of SARS-CoV-2 infection and its severity.

RESULTS

We studied 761 subjects, 371 cases, and 390 controls with a mean age of 53 years (SD, 17 years). Overall, 51% had a complete vaccination scheme, and an incomplete scheme (one dose from a scheme of two), 14%. After adjustment for age, gender, obesity, and diabetes mellitus, we found that the effectiveness of avoiding a SARS-CoV-2 infection when hospitalized with at least one vaccination dose was 71% (OR 0.29, 95% CI 0.19-0.45), that of an incomplete vaccination scheme, 67% (OR 0.33, 95% CI 0.18-0.62), and that of any complete vaccination scheme, 73% (OR 0.27, 95% CI 0.17-0.43).

CONCLUSIONS

The SARS-CoV-2 vaccination program showed effectiveness in preventing SARS-CoV-2 infection in hospitalized patients during a Delta variant outbreak.

COVID-19 Incidence Proportion as a Function of Regional Testing Strategy, Vaccination Coverage, and Vaccine Type

Introduction: The COVID-19 pandemic has become a serious challenge for humanity almost everywhere globally. Despite active vaccination around the world, the incidence proportion in different countries varies significantly as of May 2022. The reason may be a combination of demographic, immunological, and epidemiological factors. The purpose of this study was to analyze possible relationships between COVID-19 incidence proportion in the population and the types of SARS-CoV-2 vaccines used in different countries globally, taking into account demographic and epidemiological factors. Materials and methods: An initial database was created of demographic and immunoepidemiological information about the COVID-19 situation in 104 countries collected from published official sources and repository data. The baseline included, for each country, population size and density; SARS-CoV-2 testing coverage; vaccination coverage; incidence proportion; and a list of vaccines that were used, including their relative share among all vaccinations. Subsequently, the initial data set was stratified by population and vaccination coverage. The final data set was subjected to statistical processing both in general and taking into account population testing coverage. Results: After formation of the final data set (including 53 countries), it turned out that reported COVID-19 case numbers correlated most strongly with testing coverage and the proportions of vaccine types used, specifically, mRNA (V1); vector (V2); peptide/protein (V3); and whole-virion/inactivated (V4). Due to the fact that an inverse correlation was found between 'reported COVID-19 case numbers' with V2, V3, and V4, these three vaccine types were also combined into one analytic group, 'non-mRNA group' vaccines (Vnmg). When the relationship between vaccine type and incidence proportion was examined, minimum incidence proportion was noted at V1:Vnmg ratios (%:%) from 0:100 to 30:70. Maximum incidence proportion was seen with V1:Vnmg from 80:20 to 100:0. On the other hand, we have shown that the number of reported COVID-19 cases in different countries largely depends on testing coverage. To offset this factor, countries with low and extremely high levels of testing were excluded from the data set; it was then confirmed that the largest number of reported COVID-19 cases occurred in countries with a dominance of V1 vaccines. The fewest reported cases were seen in countries with a dominance of Vnmg vaccines. Conclusion: In this paper, we have shown for the first time that the level of reported COVID-19 incidence proportion depends not only on SARS-CoV-2 testing and vaccination coverage, which is quite logical, but probably also on the vaccine types used. With the same vaccination level and testing coverage, those countries that predominantly use vector and whole-virion vaccines feature incidence proportion that is significantly lower than countries that predominantly use mRNA vaccines.

Influence of age, gender, previous SARS-CoV-2 infection, and pre-existing diseases in antibody response after COVID-19 vaccination: A review

Vaccines induce specific long-term immunological memory against pathogens, preventing the worsening of diseases. The COVID-19 health emergency has caused more than 6 million deaths and started a race for vaccine development. Antibody response to COVID-19 vaccines has been investigated primarily in healthcare workers. The heterogeneity of immune responses and the behavior of this response in particular groups were still very little explored. In this review, we discuss whether antibody responses after vaccination are influenced by age, gender, previous SARS-CoV-2 infection, or pre-existing diseases.

SARS-CoV-2 in brief: from virus to prevention

The recent outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), ahighly transmissible virus with a likely animal origin, has posed major and unprecedentedchallenges to millions of lives across the affected nations of the world. This outbreak firstoccurred in China, and despite massive regional and global attempts shortly thereafter, itspread to other countries and caused millions of deaths worldwide. This review presents keyinformation about the characteristics of SARS-CoV-2 and its associated disease (namely,coronavirus disease 2019) and briefly discusses the origin of the virus. Herein, we also brieflysummarize the strategies used against viral spread and transmission.

Fear of Illness and Convenient Access to Vaccines Appear to Be the Missing Keys to Successful Vaccination Campaigns: Analysis of the Factors Influencing the Decisions of Hospital Staff in Poland concerning Vaccination against Influenza and COVID-19

The COVID-19 pandemic has lasted for two years as of 2022, and it is common knowledge that vaccines are an essential tool to mitigate the health, economic, and social fallout. Unfortunately, vaccine hesitancy is still a serious global problem, both in the general population and among healthcare workers. The authors used an original questionnaire to conduct an anonymous survey study in the University Clinical Hospital in Wrocław, Poland, in April and May of 2021 after acquiring consent from the Medical University of Wrocław, Poland Bioethical Committee. The study results demonstrate that, to a significant extent, the decisions concerning vaccinations are based on factors that are difficult to change with rational argumentation, including people’s personal opinions or beliefs concerning vaccinations and their earlier experiences with vaccinations. The study results suggest that the impregnating effect of one’s own opinions, beliefs, and experiences can be surmounted if vaccines are dispensed free and conveniently while the pathogen is irrationally and emotionally perceived as untamed and possibly severe and life threatening. It makes a significant difference as in such cases that the percentage of participants whose decisions concerning vaccination are influenced by the risks to life or health of one’s own or others rises by about 27 and 36 percent points, respectively. Therefore, in order to succeed, campaigns for vaccinations need to include strong subjective and emotional communication, appealing to negative emotions and exploiting the public’s fear of the unknown while stressing tangible and personal threats possibly resulting from acquiring a vaccine-preventable infectious disease.