Protection of homologous and heterologous boosters after primary schemes of rAd26-rAd5, ChAdOx1 nCoV-19 and BBIBP-CorV during the omicron outbreak in adults of 50 years and older in Argentina: a test-negative case-control study

La equidad en la campaña de vacunación COVID de la Provincia de Buenos Aires (Argentina): un análisis del Municipio de Quilmes

INTRODUCCIÓN

la pandemia de la COVID-19 ha acentuado las desigualdades sociales, económicas y relacionadas con la salud, afectando desproporcionadamente a las personas en situación de vulnerabilidad y perpetuando la inequidad en salud. En Argentina se implementó una campaña nacional gratuita de vacunación contra la COVID-19 con una perspectiva de equidad.

OBJETIVO

identificar desigualdades territoriales en el acceso a la vacunación contra la COVID-19 en Quilmes.

MÉTODOS

se analizó la información referida a la vacunación contra la COVID-19 de personas residentes en el Municipio. Se efectuó la georreferenciación de cada vacunatorio y de cada persona a partir del domicilio declarado en el momento de la vacunación. Para caracterizar el grado de vulnerabilidad de las personas vacunadas, a cada una se le asignó el índice de carencias múltiples (ICM) correspondiente al radio censal de residencia.

RESULTADOS

al menos el 82 % de la población completó el esquema primario de vacunación (dosis 1 y dosis 2), porcentaje que alcanzó el 97 % en los mayores de 65 años. Analizando la media de dosis aplicadas se observa algo similar con un gradiente hacia los quintiles más altos pero con una mínima diferencia entre sí, situación que también se corrobora en todos los grupos etarios.

DISCUSIÓN

no se observaron brechas significativas entre los diferentes niveles socioeconómicos. Si bien se observó un mínimo gradiente en el promedio de dosis recibidas, el tiempo de acceso a las diferentes vacunas y el porcentaje de esquemas primarios completos recibidos, las mismas tienen escasa relevancia clínica y sanitaria.

Temporary impact on medical system and effectiveness of mitigation strategies after COVID-19 policy adjustment in China: a modeling study

Background

As China amends its "zero COVID" strategy, a sudden increase in the number of infections may overwhelm medical resources and its impact has not been quantified. Specific mitigation strategies are needed to minimize disruption to the healthcare system and to prepare for the next possible epidemic in advance.

Method

We develop a stochastic compartmental model to project the burden on the medical system (that is, the number of fever clinic visits and admission beds) of China after adjustment to COVID-19 policy, which considers the epidemiological characteristics of the Omicron variant, age composition of the population, and vaccine effectiveness against infection and severe COVD-19. We also estimate the effect of four-dose vaccinations (heterologous and homologous), antipyretic drug supply, non-pharmacological interventions (NPIs), and triage treatment on mitigating the domestic infection peak.

Result

As to the impact on the medical system, this epidemic is projected to result in 398.02 million fever clinic visits and 16.58 million hospitalizations, and the disruption period on the healthcare system is 18 and 30 days, respectively. Antipyretic drug supply and booster vaccination could reduce the burden on emergency visits and hospitalization, respectively, while neither of them could not reduce to the current capacity. The synergy of several different strategies suggests that increasing the heterologous booster vaccination rate for older adult to over 90% is a key measure to alleviate the bed burden for respiratory diseases on the basis of expanded healthcare resource allocation.

Conclusion

The Omicron epidemic followed the adjustment to COVID-19 policy overloading many local health systems across the country at the end of 2022. The combined effect of vaccination, antipyretic drug supply, triage treatment, and PHSMs could prevent overwhelming medical resources.

Heterologous booster with a novel formulation containing glycosylated trimeric S protein is effective against Omicron

In this study, we evaluated the efficacy of a heterologous three-dose vaccination schedule against the Omicron BA.1 SARS-CoV-2 variant infection using a mouse intranasal challenge model. The vaccination schedules tested in this study consisted of a primary series of 2 doses covered by two commercial vaccines: an mRNA-based vaccine (mRNA1273) or a non-replicative vector-based vaccine (AZD1222/ChAdOx1, hereafter referred to as AZD1222). These were followed by a heterologous booster dose using one of the two vaccine candidates previously designed by us: one containing the glycosylated and trimeric spike protein (S) from the ancestral virus (SW-Vac 2µg), and the other from the Delta variant of SARS-CoV-2 (SD-Vac 2µg), both formulated with Alhydrogel as an adjuvant. For comparison purposes, homologous three-dose schedules of the commercial vaccines were used. The mRNA-based vaccine, whether used in heterologous or homologous schedules, demonstrated the best performance, significantly increasing both humoral and cellular immune responses. In contrast, for the schedules that included the AZD1222 vaccine as the primary series, the heterologous schemes showed superior immunological outcomes compared to the homologous 3-dose AZD1222 regimen. For these schemes no differences were observed in the immune response obtained when SW-Vac 2µg or SD-Vac 2µg were used as a booster dose. Neutralizing antibody levels against Omicron BA.1 were low, especially for the schedules using AZD1222. However, a robust Th1 profile, known to be crucial for protection, was observed, particularly for the heterologous schemes that included AZD1222. All the tested schedules were capable of inducing populations of CD4 T effector, memory, and follicular helper T lymphocytes. It is important to highlight that all the evaluated schedules demonstrated a satisfactory safety profile and induced multiple immunological markers of protection. Although the levels of these markers were different among the tested schedules, they appear to complement each other in conferring protection against intranasal challenge with Omicron BA.1 in K18-hACE2 mice. In summary, the results highlight the potential of using the S protein (either ancestral Wuhan or Delta variant)-based vaccine formulation as heterologous boosters in the management of COVID-19, particularly for certain commercial vaccines currently in use.