The COVID-19 Humoral Immunological Status Induced by CoronaVac and AstraZeneca Vaccines Significantly Benefits from a Booster Shot with the Pfizer Vaccine.

A third vaccine dose against COVID-19 is already a reality in some countries around the world. In this study, we aimed to evaluate the effectiveness of the Brazilian immunization policy for COVID-19, which involves a booster shot. Participants (n = 210) provided serum samples, which were subjected to enzyme-linked immunosorbent assay (ELISA). Immunological profiles were defined as individuals with or without previous SARS-CoV-2 infection who received at least one vaccine dose in the immunization regimens of AstraZeneca, CoronaVac, or CoronaVac plus a booster shot with Pfizer. In addition, nonvaccinated/infected individuals were also included. As main results, we observed that the numbers of infected individuals were significantly reduced among those who were vaccinated, even with one dose. This result indicates that vaccines are highly protective against COVID-19. However, we observed a significant tendency of serum level decreases of specific antibodies over the time after the second dose. In contrast, the booster shot with the Pfizer vaccine after a CoronaVac immunization regimen showed a significant increase in the specific SARS-CoV-2 IgG serum levels. Moreover, we found that vaccination induced a significantly higher humoral immunological status than only the natural infection with SARS-CoV-2. Collectively, results presented here indicate that vaccines are necessary to induce a robust immunological status, which is maintained, restored, or even improved by booster shots. IMPORTANCE COVID-19 continues to spread around the world despite significant progress in vaccine distribution and population immunity. The dynamics of the antiviral antibody response postvaccination is critical to evaluate vaccine effectiveness across different vaccine platforms and over time. In this study, we evaluate the serum levels of antiviral antibodies in patients from Brazil that received either the CoronaVac or the AstraZeneca vaccine. We found that antibody levels wane over time, vaccines induce protective immunity, and humoral immunity is enhanced with a third vaccine dose. This study reveals that the COVID-19 humoral immunological status induced by vaccines significantly benefits from a booster shot.

Anti-dengue Vaccines: From Development to Clinical Trials.

Dengue Virus (DENV) is an arbovirus (arthropod-borne virus). Four serotypes of DENV are responsible for the infectious disease called dengue that annually affects nearly 400 million people worldwide. Although there is only one vaccine formulation licensed for use in humans, there are other vaccine formulations under development that apply different strategies. In this review, we present information about anti-dengue vaccine formulations regarding development, pre-clinical tests, and clinical trials. The improvement in vaccine development against dengue is much needed, but it should be considered that the correlate of protection is still uncertain. Neutralizing antibodies have been proposed as a correlate of protection, but this ignores the key role of T-cell mediated immunity in controlling DENV infection. It is important to confirm the accurate correlate of protection against DENV infection, and also to have other anti-dengue vaccine formulations licensed for use.