The global supply of COVID-19 vaccines remains limited. An understanding of the immune response that is predictive of protection could facilitate rapid licensure of new vaccines. Data from a randomized efficacy trial of the ChAdOx1 nCoV-19 (AZD1222) vaccine in the United Kingdom was analyzed to determine the antibody levels associated with protection against SARS-CoV-2. Binding and neutralizing antibodies at 28 days after the second dose were measured in infected and noninfected vaccine recipients. Higher levels of all immune markers were correlated with a reduced risk of symptomatic infection. A vaccine efficacy of 80% against symptomatic infection with majority Alpha (B.1.1.7) variant of SARS-CoV-2 was achieved with 264 (95% CI: 108, 806) binding antibody units (BAU)/ml: and 506 (95% CI: 135, not computed (beyond data range) (NC)) BAU/ml for anti-spike and anti-RBD antibodies, and 26 (95% CI: NC, NC) international unit (IU)/ml and 247 (95% CI: 101, NC) normalized neutralization titers (NF50) for pseudovirus and live-virus neutralization, respectively. Immune markers were not correlated with asymptomatic infections at the 5% significance level. These data can be used to bridge to new populations using validated assays, and allow extrapolation of efficacy estimates to new COVID-19 vaccines.

Objective: To determine the safety, immunogenicity and efficacy of two doses of rotavirus vaccine in healthy Brazilian infants. Methods: A randomized, multicenter, double-blind, placebo-controlled trial was conducted in Brazil, Mexico and Venezuela. Infants received two oral doses of vaccine or placebo at 2 and 4 months of age, concurrently with routine immunizations, except for oral poliomyelitis vaccine (OPV). This paper reports results from Belém, Brazil, where the number of subjects per group and the viral vaccine titers were: 194 (10 4.7 focus forming units-FFU), 196 (10 5.2 FFU), 194 (10 5.8 FFU) and 194 (placebo). Anti-rotavirus (anti-RV) antibody response was assessed in 307 subjects. Clinical severity of gastroenteritis episodes was measured using a 20-point scoring system with a score of ≥ 11 defined as severe GE. Results: The rates of solicited general symptoms were similar in vaccine and placebo recipients. At 2 months after the second dose, a serum IgA response to RV occurred in 54.7 to 74.4% of vaccinees. No interference was seen in the immunogenicity of routine vaccines. Vaccine efficacy against any rotavirus gastroenteritis (RVGE) was 63.5% (95%CI 20.8-84.4) for the highest concentration (10 5.8 FFU). Efficacy was 81.5% (95%CI 44.5-95.4) against severe RVGE. At its highest concentration (10 5.8 FFU), RIX4414 provided 79.8% (95%CI 26.4-96.3) protection against severe RVGE by G9 strain. Conclusions: RIX4414 was highly immunogenic with a low reactogenicity profile and did not interfere with seroresponse to diptheria, tetanus, pertussis, hepatitis B and Hib antigens. Two doses of RIX4414 provided significant protection against severe GE caused by RV. J Pediatr (Rio J). 2007;83(3):217-224: Rotavirus, gastroenteritis, vaccine, efficacy.

The seroprevalence of hepatitis B was investigated in over 12,000 subjects in six countries of Latin America: Argentina, Brazil, Chile, the Dominican Republic, Mexico, and Venezuela. Each study population was stratified according to age, gender, and socioeconomic status. Antibodies against hepatitis B core antigen (anti-HBc) were measured in order to determine hepatitis B infection. The highest overall seroprevalence was found in the Dominican Republic (21.4%), followed by Brazil (7.9%), Venezuela (3.2%), Argentina (2.1%), Mexico (1.4%), and Chile (0.6%). In all the countries an increase in seroprevalence was found among persons 16 years old and older, suggesting sexual transmission as the major route of infection. In addition, comparatively high seroprevalence levels were seen at an early age in the Dominican Republic and Brazil, implicating a vertical route of transmission.

Terminating the SARS-CoV-2 pandemic relies upon pan-global vaccination. Current vaccines elicit neutralizing antibody responses to the virus spike derived from early isolates. However, new strains have emerged with multiple mutations: P.1 from Brazil, B.1.351 from South Africa and B.1.1.7 from the UK (12, 10 and 9 changes in the spike respectively). All have mutations in the ACE2 binding site with P.1 and B.1.351 having a virtually identical triplet: E484K, K417N/T and N501Y, which we show confer similar increased affinity for ACE2. We show that, surprisingly, P.1 is significantly less resistant to naturally acquired or vaccine induced antibody responses than B.1.351 suggesting that changes outside the RBD impact neutralisation. Monoclonal antibody 222 neutralises all three variants despite interacting with two of the ACE2 binding site mutations, we explain this through structural analysis and use the 222 light chain to largely restore neutralization potency to a major class of public antibodies.

No abstract

No abstract

No abstract

ResumoObjetivos: A varicela tem conseqüências mais graves em adolescentes e adultos. Recentes relatos da Europa e da Ásia mostram um número crescente de adolescentes e adultos jovens soronegativos. Como são poucos os dados sobre a prevalência de anti-VZV no Brasil e com o objetivo de definir estratégias para a imunização contra a varicela, realizamos um estudo de soroprevalência para o VZV (vírus varicela zoster) em diferentes partes do Brasil.Métodos: Este estudo soroepidemiológico, transversal e populacional foi realizado em quatro diferentes regiões do Brasil. A população estudada foi estratificada por sexo, idade e situação socioeconômica. Anticorpos Ig G, anti-VZV foram analisados pelo método ELISA.Resultados: Foram incluídos no estudo 3.879 indivíduos de 1 a 40 anos. A taxa de soropositividade do anti-VZV em todos os grupos etários e centros no Brasil foi de 85,4 %. Evidenciou-se uma forte correlação com a idade. Especialmente no Sudeste e Sul, a soroprevalência foi menor no grupo etário de 1-5 anos (44,5% e 57,8%, respectivamente). Na região Norte esta taxa foi de 88,9%. No geral, a infecção pelo VZV foi independente do nível socioeconômico, entretanto nos grupos etários jovens (1-10 anos) a soroprevalência foi significativamente menor nas classes alta/média, na maioria das regiões. A história clínica de varicela se correlacionou com a soropositividade anti-VZV, tendo um valor preditivo de 95,1%.Conclusões: Na pré-adolescência, uma proporção substancial da população brasileira é susceptível à varicela e uma parcela considerável de adolescentes e adultos jovens permanecem soronegativos e, conseqüentemente, em risco. AbstractObjectives: Varicella has more serious consequences in adolescents and adults. Recent reports from Europe and Asia show an increasing number of adolescents and young adults being seronegative. As there is only limited data on varicella zoster virus (VZV) seroprevalence in Brazil and to facilitate the strategy for varicella vaccination we conducted a VZV seroprevalence study in Brazil.Methods: This population-based, cross sectional seroepidemiology study was performed in 4 different regions of Brazil. The studied population was stratified according to gender, age and socioeconomic status. VZV IgG antibodies were analyzed by ELISA.Results: 3,879 subjects aged 1-40 years were included into the study. The overall anti-VZV seropositivity rate across all age groups and centers in Brazil was 85.4%. There was a strong age relationship. Especially in the South East and South seroprevalence was low in the age group 1-5 years (44.5% and 57.8%, respectively) while in the North the rate was 88.9%. Overall, Varicella infection was independent of the socioeconomic level, but in the youngest age groups (1-10 years) seroprevalence rates were significantly lower in the high/medium socioeconomic class for most regions. Clinical history of chickenpox correlates well with anti-VZV seropositivity with a predictive value of 95.1%Conclusions: In preadolescence a substantial proportion of the Brazilian populat...