Cobertura de vacunación contra COVID-19 e influenza en personal de salud y administrativo en Paraguay

Introducción: A nivel mundial, la cobertura de vacunación contra el COVID-19, así como contra la influenza es baja tanto en la población general como en los profesionales de la salud a pesar de que la vacuna es gratuita y obligatoria en el personal sanitario. Objetivo: Describir la cobertura de vacunación contra el COVID -19, y la influenza en personal de salud y administrativo de un hospital de referencia del Ministerio de Salud Pública y Bienestar Social en el periodo 2021-2022. Metodología: Estudio observacional descriptivo de corte trasverso. Se hizo la revisión de los registros del personal sanitario y administrativo del centro vacunatorio del Hospital Nacional de Itauguá de la campaña vacunal contra el COVID-19 y de anti-influenza en el periodo 2021- 2022. Resultados: De los 3.586 funcionarios, 999 (27,9 %) eran médicos, 1494 (41,7 %) personal de enfermería, 366 (10,2 %) otra categoría de personal sanitario, y 727 (20,3 %) personal administrativo. En forma global, el 86,5 % de los funcionarios recibió por lo menos las dos dosis que constituyen el esquema primario y el 73 % la dosis de refuerzo. El 2,1 % del personal no recibió ninguna dosis de vacuna anti covid-19, la cifra fue mayor en el personal administrativo (4,8 %). La cobertura de vacunación contra la influenza fue de 20 % en el 2021 y 25 % en el 2022. Discusión: Si bien cobertura de vacunación anti-COVID-19 fue comparable a otros países, la vacunación contra la influenza fue muy baja. Es urgente implementar estrategias dirigidas a aumentar la percepción de riesgo y aceptabilidad de las vacunas obligatorias para el personal sanitario.

Introduction: Worldwide, vaccination coverage against COVID-19, as well as against influenza, is low both in the general population and in health professionals, despite the fact that the vaccine is free and mandatory for health personnel. Objective: To describe the COVID -19 and influenza vaccination coverage in health and administrative personnel of a reference hospital of the Ministry of Public Health and Social Welfare in the period 2021-2022. Methods: Cross-sectional descriptive observational study. Charts of the health and administrative personnel of the vaccination center of the Itauguá National Hospital of the COVID-19 and influenza vaccination campaign in the period 2021-2022 were reviewed. Results: Of the 3,586 personnel, 999 (27.9%) were medical personnel, 1,494 (41.7%) nursing personnel, 366 (10.2%) other category of health personnel, and 727 (20.3%) administrative personnel. Overall, 86.5% of the employees received at least the two doses that constitute the primary schedule and 73% the booster dose; 2.1% of the staff did not receive any dose of the anti COVID-19 vaccine, which was higher in the administrative staff (4.8%). Influenza vaccination coverage was 20% in 2021 and 25% in 2022. Discussion: Even though the vaccination coverage of anti-COVID-19 was comparable to other countries, vaccination anti-influenza was very low. It is urgent to implement strategies aimed at increasing the perception of risk and acceptability of mandatory vaccines for health personnel.

Seroprevalencia del SARS-CoV-2 en los pacientes con enfermedades inmunomediadas en tratamiento con terapias biológicas y sintéticos dirigidos / Seroprevalence of SARS-CoV-2 antibodies in patients with immune-mediated inflammatory diseases treated with biological and synthetic targeted therapies

INTRODUCCIÓN: La seroprevalencia del SARS-CoV-2 en las enfermedades inflamatorias inmunomediadas (IMID) sigue siendo fuente de controversia. OBJETIVO: Comparar la seroprevalencia de anticuerpos (Ac) anti SARS-CoV-2 en pacientes con IMID en tratamientos con fármacos antirreumáticos modificadores de la enfermedad biológicos (FAMEb) o sintéticos dirigidos (FAMEsd) frente a un grupo de personas sin IMID. MÉTODOS: Estudio de pacientes con IMID y tratamientos con FAMEb y FAMEsd y de individuos sin IMID. Mediante la técnica de inmunoensayo por quimioluminiscencia indirecta, se determinaron las serologías IgG frente al SARS-CoV-2 entre octubre/2020 y mayo/2021. RESULTADOS: Se estudiaron 1.100 sujetos, 550 pacientes con IMID y 550 personas sin IMID. Se observó una seroprevalencia de 16% (88/550) en los pacientes frente a 19,3% (106/550) en el grupo de personas sin IMID, sin significación estadística (OR 0,790 [IC 95% 0,558-1,118]). Comparando los tratamientos con FAMEb o FAMEsd, se observó una tendencia a una menor seroprevalencia con rituximab, en relación con los individuos sin IMID (OR 0,296 [IC 95% 0,0871,007]). Asimismo, se encontró menor seroprevalencia en los pacientes que además de su FAMEb recibían tratamiento con metotrexato, en comparación con el grupo de personas sin IMID (OR 0,432 [IC 95% 0,223-0,835]). CONCLUSIONES: Las IMID en tratamiento con FAMEb o FAMEsd no influyen en la seroprevalencia frente al SARS-CoV-2 de los pacientes. El tratamiento concomitante con metotrexato disminuye de forma significativa la seroprevalencia en estos pacientes.

BACKGROUND: The seroprevalence of SARS-CoV-2 in immunemediated inflammatory diseases (IMID) remains controversial. AIM: To compare the seroprevalence of antibodies (Ab) to SARS-CoV-2 in patients with IMID receiving treatment with biological diseasemodifying antirheumatic drugs (bDMARD) or targeted synthetic (tsDMARD) versus a group of people without IMID. METHODS: Study of patients with IMID and treatments with bDMARD and tsDMARD and individuals without IMID. IgG serology against SARS-CoV-2 was measured using the two-step sandwich immunoassay technique by indirect chemiluminescence between October 2020 and May 2021. RESULTS: A total of 1100 subjects were studied, 550 patients with IMID and 550 persons without IMID. A seroprevalence of 16% (88/550) was observed in patients versus 19.3% (106/550) in the group of people without IMID, without statistical significance (OR 0.790 [95% CI 0.558-1.118]). Comparing the treatments with bD- MARD or tsDMARD, there was a tendency to lower seroprevalence with rituximab, in relation to individuals without IMID (OR 0.296 [95% CI 0.087-1.007]). In addition, lower seroprevalence was found in patients who received methotrexate treatment in addition to their bDMARD, compared to the group of individuals without IMID (OR 0.432 [95% CI 0.223-0.835]). CONCLUSIONS: IMIDs in treatment with bDMARDs or tsDMARDs do not influence the seroprevalence against SARS-CoV-2 in patients. Concomitant treatment with methotrexate significantly decreased seroprevalence in these patients.

Flavonoids from the roots and rhizomes of Sophoratonkinensis and their in vitro anti-SARS-CoV-2 activity / 中国天然药物

Acute respiratory infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) had caused a global pandemic since 2019, and posed a serious threat to global health security. Traditional Chinese medicine (TCM) has played an indispensable role in the battle against the epidemic. Many components originated from TCMs were found to inhibit the production of SARS-CoV-2 3C-like protease (3CLpro) and papain-like protease (PLpro), which are two promising therapeutic targets to inhibit SARS-CoV-2. This study describes a systematic investigation of the roots and rhizomes of Sophora tonkinensis, which results in the characterization of 12 new flavonoids, including seven prenylated flavanones (1-7), one prenylated flavonol (8), two prenylated chalcones (9-10), one isoflavanone (11), and one isoflavan dimer (12), together with 43 known compounds (13-55). Their structures including the absolute configurations were elucidated by comprehensive analysis of MS, 1D and 2D NMR data, and time-dependent density functional theory electronic circular dichroism (TDDFT ECD) calculations. Compounds 12 and 51 exhibited inhibitory effects against SARS-CoV-2 3CLpro with IC50 values of 34.89 and 19.88 μmol·L-1, repectively while compounds 9, 43 and 47 exhibited inhibitory effects against PLpro with IC50 values of 32.67, 79.38, and 16.74 μmol·L-1, respectively.

Vacunación en pacientes con inmunodeficiencias primarias / Vaccination in patients with primary immunodeficiciencies / Vacinação em pacientes com imunodeficiências primárias

RESUMEN En los pacientes inmunocomprometidos resulta primordial una correcta inmunización porque tienen mayor riesgo de infección. Se realizó una investigación observacional-descriptiva-retrospectiva, para describir el proceso de vacunación de los pacientes con inmunodeficiencias primarias en Granma, entre el 2012 y 2021, en una muestra de 39 casos. Los datos se recolectaron de historias clínicas y tarjetas de vacunación. Se emplearon las frecuencias absolutas y relativas y el procesador estadístico SPSS 25. La BCG se administró al 100% de los pacientes. En el 85% de los menores de 10 años, la vacuna PRS se contraindicó oportunamente y la anti-polio oral se administró a 10 pacientes. Las vacunas DT y DPT, se aplicaron al 65 y 95%de los pacientes respectivamente. Cinco niños recibieron vacuna anti-neumocóccica y el 94.87% inmunoprofilaxis para SARS CoV-2. La Inmunodeficiencia Variable Común y la BCG, fueron la IDP y la vacuna respectivamente, con más dificultad para su correcto manejo.

ABSTRACT In immunocompromised patients, correct immunization is essential because they have a higher risk of infection. An observational-descriptive-retrospective research was carried out to describe the vaccination process of patients with primary immunodeficiencies in Granma, between 2012 and 2021, in a sample of 39 cases. The data was collected from medical records and vaccination cards. Absolute and relative frequencies and the SPSS 25 statistical processor were used. BCG was administered to 100% of the patients. In 85% of children under 10 years of age, the PRS vaccine was opportunely contraindicated and the oral anti-polio vaccine was administered to 10 patients. The DT and DPT vaccines were applied to 65 and 95% of the patients, respectively. Five children received anti-pneumococcal vaccine and 94.87% immunoprophylaxis for SARS CoV-2. Common Variable Immunodeficiency and BCG were the PID and the vaccine, respectively, with more difficulty for their correct management.

RESUMO Em pacientes imunocomprometidos, a imunização adequada é essencial porque eles têm maior risco de infecção. Foi realizada uma pesquisa observacional-descritiva-retrospectiva para descrever o processo de vacinação de pacientes com imunodeficiências primárias em Granma, entre 2012 e 2021, em uma amostra de 39 casos. Os dados foram coletados nos prontuários e cartões de vacinação. Foram utilizadas frequências absolutas e relativas e o processador estatístico SPSS 25. A BCG foi administrada em 100% dos pacientes. Em 85% das pessoas com menos de 10 anos, a vacina contra-vacina contra-vacina oral foi contraindicada e a vacina anti poliomielite oral foi administrada a 10 pacientes. As vacinas DT e DPT foram aplicadas a 65% e 95% dos pacientes, respectivamente. Cinco crianças receberam vacina pneumocócica e 94,87% imunoprofilaxia para SARS CoV-2. A Imunodeficiência Variável Comum e o BCG foram o IDP e a vacina, respectivamente, com maior dificuldade para o seu manejo correto.

Multi System Inflammatory Syndrome In Neonates (MIS-N): A Case Report

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection during pregnancy may increase the risk of stillbirth, neonatal death, preterm birth, low birth weight, fetal distress, and neonatal asphyxia. Vertical transmission of SARS-CoV-2 is under investigation. Afew reports suggest the possibility of SARS-CoV-2 transmission from mothers to their neonates. The SARS-CoV-2 virus was reported as one of the rare causes of fetal inflammatory response syndrome (FIRS) and is associated with multisystem inflammatory syndrome in children (MIS-C).

Serological follow up of positive SARS-CoV-2 cases / Seguimiento serológico de casos positivos a SARS-CoV-2

Abstract: Objective: To describe the humoral response in a cohort with mild and asymptomatic SARS-CoV-2 infection previously identified in a community-based serological survey. Materials and methods: This study was an observational follow up of 193 subjects previously identified with positive anti-SARS-CoV-2 antibodies invited for a second test 112 days after the first sampling. All completed a standardized electronic questionnaire. IgM/IgG antibodies were determined using a qualitative IgM/IgG chemiluminescent immunoassay. Results: Among the 193 eligible subjects, a total of 174 (90%) attended the follow-up visit, and their serum samples were tested. Of the samples, 171 (98.3%) were still positive, and 3 (1.7%) were negative. Also, the cut-off index (COI) value of the immunoassay significantly increased from the first to the second test (P <0.001). Conclusions: Our findings support a sustained humoral response in individuals with mild and asymptomatic SARS-CoV-2 infection up to 112 days after a positive serologic baseline test, accompanied by increasing antibody titers.

Resumen: Objetivo: Describir la respuesta humoral en una cohorte con una infección leve o asintomática por SARS-CoV-2, previamente identificada en una encuesta serológica comunitaria. Material y métodos: Se realizó un seguimiento observacional de 193 individuos previamente identificados con anticuerpos IgM/IgG anti-SARS-CoV-2 invitados 112 días después de una determinación serológica inicial. Todos los participantes completaron un cuestionario electrónico estandarizado. Se determinaron los anticuerpos IgM/IgG mediante un inmunoensayo quimioluminiscente cualitativo. Resultados: De entre los 193 sujetos elegibles, 174 (90%) acudieron al seguimiento. De las muestras, 171 (98.3%) eran positivas y 3 (1.7%) negativas. Además, el valor de COI del inmunoenasayo se incrementó al comparar la primera y segunda determinación (P <0.001). Conclusiones: Los presentes resultados apoyan una respuesta humoral sostenida en individuos con infección por SARS-CoV-2 con síntomas leves o asintomática hasta 112 días después de una prueba serológica positiva, acompañada de incremento en los títulos de anticuerpos.

Seric IgG anti-SARS-CoV-2 pre- and post- Covid-19 pandemic from Mexican asymptomatic subjects / IgG sérica anti-SARS-CoV-2 pre y post pandemia de Covid-19 en mexicanos asintomáticos

Abstract: Objective: To detect serum IgG anti-SARS-CoV-2 in pre- and post- Covid-19 pandemic in Mexican asymptomatic subjects in order to know the degree of viral dispersion. Materials and methods: Association of serum IgG antibodies (determined by ELISA) to sociodemographic and clinical data or contact with Covid-19 cases in three groups of subjects: 1) Covid-19 pre-pandemic blood donors (n= 538); 2) Covid-19 post-pandemic blood donors (n= 243); 3) Covid-19 post-pandemic neurological patients (n= 312). None of the subjects studied had been vaccinated. Results: The positive rate of IgG anti-SARS-CoV-2 was notably higher in participants recruited during the pandemic (donors, 29.6%; neurological patients, 15.7%) than in those recruited pre-pandemic (donors 0.6%) (p <0.001). Other conditions associated to antibody positivity were being a worker in sales or services, or having had previous contact with people with Covid-19, for donnors and neurological patients, and having diabetes mellitus, for neurological patients. Higher positivity levels of anti-SARS-CoV-2 IgG were found in females than in males. The highest proportion of subjects with anti-SARS-CoV-2 antibodies was found in central Mexico. Conclusions: The dispersion of SARS-CoV-2 in asymptomatic, unvaccinated subjects (donors and neurological patients) recruited in a Mexican health institution, who work in sales or services or had previously had contact with Covid-19 patients is 16 to 30%. The level of positivity for anti-SARS-CoV-2 IgG is higher in females than in males. SARS-CoV-2 antibody seroprevalence follow-up studies must be favored among the general population, being mandatory for donors.

Resumen: Objetivo: Detectar IgG sérica anti-SARS-CoV-2 antes y después de la pandemia de Covid-19 en sujetos mexicanos asintomáticos, con la intención de conocer el grado de dispersión viral. Material y métodos: Se analizó la asociación de anticuerpos IgG séricos (determinados por ELISA), datos sociodemográficos y clínicos y contacto con casos de Covid-19 en tres grupos de sujetos: 1) donadores de sangre reclutados antes de la pandemia de Covid-19 (n= 538); 2) donadores (n= 243) y 3) pacientes neurológicos (n= 312) reclutados durante la pandemia de Covid-19. Ninguno de los sujetos estudiados había sido vacunado. Resultados: La tasa de positividad de IgG anti-SARS-CoV-2 fue notablemente mayor en los participantes reclutados durante la pandemia (donadores, 29.6%; pacientes neurológicos, 15.7%) que en los reclutados prepandemia (donadores 0.6%). Otras condiciones asociadas con positividad de anticuerpos fueron trabajar en ventas o servicios, o haber tenido contacto previo con pacientes Covid-19, en donadores y pacientes neurológicos, y haber tenido diabetes mellitus, en pacientes neurológicos. Se encontraron mayores niveles de positividad de IgG anti-SARS-CoV-2 en mujeres que en hombres. La mayor proporción de sujetos con anticuerpos anti-SARS-CoV-2 procedía del centro de México. Conclusiones: La dispersión del SARS-CoV-2 en sujetos asintomáticos, no vacunados (donadores y pacientes neurológicos), reclutados en una institución de salud mexicana, que trabajan en ventas o servicios, o tienen contacto previo con pacientes Covid-19 es de 16 a 30%. El nivel de positividad de IgG anti-SARS-CoV-2 es más alto en mujeres que en hombres. Los estudios de seguimiento de la seroprevalencia del SARS-CoV-2 deben favorecerse en la población general, siendo obligatorios en los donadores.

Evaluación de ensayos ultramicroanalíticos para la detección de anticuerpos contra el SARS-CoV-2 / Evaluation of ultramicroanalytic assays to detect antibodies against SARS-CoV-2

Introducción: En el presente trabajo se muestran los resultados de la validación de los ensayos serológicos in vitro para la detección de anticuerpos IgM, IgG y anticuerpos totales contra el SARS-CoV-2 UMELISA SARS-CoV-2 IgM, UMELISA ANTI-SARS-CoV-2 y UMELISA SARS-CoV-2 IgG desarrollados por el Centro de Inmunoensayo (CIE). Métodos: Se utilizaron paneles de muestras de suero de individuos negativos y de casos confirmados de COVID-19 para determinar el desempeño analítico de cada ensayo. Resultados: La especificidad clínica de los ensayos UMELISA SARS-CoV-2 IgM, UMELISA ANTI-SARS-CoV-2 y UMELISA SARS-CoV-2 IgG fue del 100 por ciento en todos los ensayos y la especificidad analítica fue de 100 por ciento para los dos primeros ensayos y del 93,1 por cientopara el último. La sensibilidad clínica fue de 64,3, 80,8 y 97,5 por ciento, respectivamente. El valor predictivo positivo fue de 100 por ciento en todos los ensayos, en tanto que el negativo osciló entre 83,3 y 95,2 por ciento. La concordancia fluctuó entre 92,4 y 96,9 por ciento y el índice kappa de todos los ensayos fue muy bueno. La sensibilidad de los ensayos se incrementó a 82,76, 96,5 y 100 por ciento, respectivamente, en las muestras de suero colectadas con más de 14 días de iniciado el cuadro clínico. Conclusiones: Los ensayos demostraron una elevada sensibilidad y especificidad, lo que permite contar con herramientas basadas en una tecnología desarrollada en Cuba que posibilita la realización de estudios serológicos, vigilancia epidemiológica y de otro tipo, incluyendo los relacionados con vacunas en una plataforma con amplia distribución nacional(AU)

Introduction: This paper shows the results obtained in the validation of in vitro serological assays to detect IgM, IgG antibodies, and total antibodies against SARS-CoV-2 UMELISA SARS-CoV-2 IgM, UMELISA ANTI-SARS-CoV-2 and UMELISA SARS-CoV-2 IgG developed by the Immunoassay Center. Methods: Panels of serum samples from negative and COVID-19 confirmed patients were used to determine the analytical performance of each assay. Results: UMELISA SARS-CoV-2 IgM, UMELISA ANTI-SARS-CoV-2 and UMELISA SARS-CoV-2 IgG assays demonstrated 100 percent clinical specificity for all assays; and 100 percent analytical specificity for the first two assays, and 93.1 percent for the last one. Clinical sensitivity was 64.3 percent, 80.8 percent and 97.5 percent, respectively. The positive predictive value was 100 percent in all assays, while the negative predictive value ranged from 83.3 percent to 95.2 percent. Concordance varied from 92.4 percent to 96.9 percent, and kappa index in every assay was very good. Assays sensitivity increased to 82.7 percent, 96.5 percent and 100 percent, respectively for serum samples collected more than 14 days after onset of the symptoms. Conclusions: The assays demonstrated high sensitivity and specificity, which allows us to have Cuban technology-based tools for serological, epidemiological surveillance, and other types of studies, including those related to vaccines on a platform with wide national distribution(AU)

Serological evaluation of immune effect of inactivated COVID-19 vaccine in adult population in Deqing County， Huzhou City， Zhejiang Province / 上海预防医学

ObjectiveTo investigate the specific anti-SARS-CoV-2 antibody in adults and above after initial vaccination with inactivated COVID-19 vaccine， and determine the influencing factors. MethodsIn this study， residents aged 18 and above who had completed two doses of inactivated COVID-19 vaccine in Deqing County， Huzhou City， Zhejiang Province were included. Information such as gender， age， type of vaccine and vaccination time were collected， and serum specimens were sampled. Anti-SARS-CoV-2 receptor binding domain （RBD） antibody was quantitatively examined by enzyma-linked immunosorbent assay （ELISA） and influencing factors were determined. ResultsThe median concentration of anti-SARS-CoV-2 IgG antibody in the residents vaccinated with an inactivated booster vaccine was higher than that in those vaccinated with only two doses of COVID-19 vaccine or single dose （P<0.05）. The median concentration of IgG antibody in males was 9.73 （4.01‒23.70） RU‧mL-1， lower than 17.76 （7.07‒49.23） RU‧mL-1 in females （P<0.05）. The median concentration in the residents vaccinated with BBIBP-CorV （Sinopharm） was 6.53 （0.97‒13.69） RU‧mL-1， which was lower than that in those vaccinated with CoronaVac （Sinovac） that was 17.29 （8.54‒43.73） RU‧mL-1 （P<0.05）. The median concentration in those with BBIBP-CorV was also lower than 12 （5.45‒40.06） RU‧mL-1 in those with heterologous booster vaccine （P<0.05）. The median concentration was 9.73 （3.83‒23.63） RU‧mL-1 in the residents with an interval of more than 6 months from the second dose， which was lower than 14.66 （6.36‒35.98） RU‧mL-1 in those with an interval of 3‒6 months （P<0.05）. Moreover， immune effect was better in females （χ²=16.464， P<0.05）， 18‒45 years（χ²=7.158， P<0.05）， and those vaccinated with CornaVac （χ²=49.637， P<0.05）， while decreased in those with an interval of more than 6 months from the second dose （χ²=8.447， P<0.05）. ConclusionGender， age， and type of vaccine may affect the effect of immunization. The COVID-19 vaccination shows an acceptable immunogenicity in adults； however， it declines in 6 months after vaccination. It warrants strengthening the booster vaccination to maintain the immune response.

In Silico Screening of Natural Products as Potential Inhibitors of SARS-CoV-2 Using Molecular Docking Simulation / 中国结合医学杂志

OBJECTIVE@#To explore potential natural products against severe acute respiratory syndrome coronavirus (SARS-CoV-2) via the study of structural and non-structural proteins of human coronaviruses.@*METHODS@#In this study, we performed an in-silico survey of 25 potential natural compounds acting against SARS-CoV-2. Molecular docking studies were carried out using compounds against 3-chymotrypsin-like protease (3CLPRO), papain-like protease (PLPRO), RNA-dependent RNA polymerase (RdRp), non-structural protein (nsp), human angiotensin converting enzyme 2 receptor (hACE2R), spike glycoprotein (S protein), abelson murine leukemia viral oncogene homolog 1 (ABL1), calcineurin-nuclear factor of activated T-cells (NFAT) and transmembrane protease serine 2.@*RESULTS@#Among the screened compounds, amentoflavone showed the best binding affinity with the 3CLPRO, RdRp, nsp13, nsp15, hACE2R. ABL1 and calcineurin-NFAT; berbamine with hACE2R and ABL1; cepharanthine with nsp10, nsp14, nsp16, S protein and ABL1; glucogallin with nsp15; and papyriflavonol A with PLPRO protein. Other good interacting compounds were juglanin, betulinic acid, betulonic acid, broussooflavan A, tomentin A, B and E, 7-methoxycryptopleurine, aloe emodin, quercetin, tanshinone I, tylophorine and furruginol, which also showed excellent binding affinity towards a number of target proteins. Most of these compounds showed better binding affinities towards the target proteins than the standard drugs used in this study.@*CONCLUSION@#Natural products or their derivatives may be one of the potential targets to fight against SARS-CoV-2.

Maternal vaccination as an additional approach to improve the protection of the nursling: Anti-infective properties of breast milk

Abstract Human milk constitutes a secretion with unique functions of both nourishing the nursling and providing protection against enteric and respiratory infections, mainly due to its content of secretory IgA antibodies but also due to the presence of a plethora of bioactive factors. Specific IgA antibodies are produced locally by plasma cells derived from B lymphocytes that migrate from other mucosae to the mammary gland during lactation, particularly from the gastrointestinal and respiratory tracts. Therefore, here, the authors will provide a comprehensive review of the content and functions of different nutritional and bioactive anti-infectious components from breast milk, such as oligosaccharides, lactoferrin, haptocorrin, α-lactalbumin, k-casein, lysozyme, lactoperoxidase, mucin, fatty acids, defensins, cytokines and chemokines, hormones and growth factors, complement proteins, leukocytes and nucleic acids, including microRNAs, among many others, and the induction of antibody responses in breast milk after maternal vaccination with several licensed vaccines, including the anti-SARS-CoV-2 vaccine preparations used worldwide. Currently, in the midst of the pandemic, maternal vaccination has re-emerged as a crucial source of passive immunity to the neonate through the placenta and breastfeeding, considering that maternal vaccination can induce specific antibodies if performed during pregnancy and after delivery. There have been some reports in the literature about milk IgA antibodies induced by bacterial antigens or inactivated virus vaccines, such as anti-diphtheria-tetanus-pertussis, anti-influenza viruses, anti-pneumococcal and meningococcal polysaccharide preparations. Regarding anti-SARS-CoV-2 vaccines, most studies demonstrate elevated levels of specific IgA and IgG antibodies in milk with virus-neutralizing ability after maternal vaccination, which represents an additional approach to improve the protection of the nursling during the entire breastfeeding period.