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Background: As of September 2022, nearly 1.3 billion doses of COVID-19 vaccine products have been administered in Latin America and the Caribbean, where 27% of global COVID-19 deaths have occurred. This study aimed to estimate the effectiveness of COVID-19 vaccines against lab-confirmed COVID-19 related hospitalizations and deaths among adults in Argentina, Brazil, Chile, and Colombia., Methods: Using a test-negative case control design, we evaluated the effectiveness of a primary vaccination series considering six COVID-19 vaccine products (Sputnik V, mRNA-1273, CoronaVac, ChAdOx1, BNT162b2, Ad26.COV2.S) against lab-confirmed COVID-19 hospitalizations and deaths among 83,708 hospitalized adults from February-December, 2021. Data from hospitalization records, COVID surveillance, and vaccination registries were used. Vaccine effectiveness was estimated using logistic regression ((1-OR) x 100)., Findings: The average age of participants was 56.7 (SD = 17.5), and 45,894 (54.8%) were male. Adjusted VE (aVE) estimates for full vaccination against hospitalization were 82% for mRNA-1273 (95% confidence interval (CI) = -30 to 98%), 76% (71%-81%) for BNT162b2, 65% (61-68%) for ChAdOx1, 57% (10-79%) for Sputnik V, 53% (50-56%) for CoronaVac, and 46% (23-62%) for Ad26.COV2.S. Estimates, particularly for CoronaVac, varied by variant. Decreasing aVE was estimated as age increased, particularly for CoronaVac and ChAdOx1. aVE estimates against death were generally higher, with 100% (CI not estimated) for mRNA-1273, 82% (69-90%) for BNT162b2, 73% (69-77%) for ChAdOx1, 65% (60-67%) for CoronaVac, 38% (-75 to 78%) for Sputnik V, 6% (-58 to 44%) for Ad26.COV2.S., Interpretation: Primary series vaccination with available COVID-19 vaccine products was effective against COVID-19 hospitalization and mortality. Effectiveness varied by product and declined with increasing age., Funding: This study was funded by the Pan-American Health Organization (PAHO, World Health Organization (WHO)). PAHO convened and led the study implementation., Competing Interests: CMT received research suppport fees to support this work. CJ and RK were hired consultant to support study design, implementation, and analysis. CD has received payment or honoraria from Merck, Sanofi, Janssen, Pfizer., (© 2023 Published by Elsevier Ltd.)

Background: In January 2018, Ecuador changed its routine immunization schedule by replacing one full dose of inactivated poliovirus vaccine (IPV) administered intramuscularly at 2 months of age with two doses of fractional IPV (1/5th of full dose, fIPV) administered intradermally at 2 and 4 months of age; and bivalent oral poliovirus vaccine (serotypes 1 and 3, bOPV) continues to be used. We compared seroprevalence and titres of polio antibodies achieved by the past and the current immunization schedules., Methods: This was a cross-sectional serological survey in children in Ecuador who received bOPV and either one IPV dose in 2017 or two fIPV doses in 2018. One blood sample was collected between October 2020 and March 2021 and analysed for presence of poliovirus neutralizing antibodies at CDC, Atlanta by microneutralization assay., Findings: We obtained 321 analysable samples from 329 (97·6%) enrolled children (160 received IPV and 161 fIPV). For serotype 2, seroprevalence was 50·0% (CI95%= 44·2-55·8%) for IPV and 83·2% (CI95%=78·5-87·1%) for fIPV recipients (p<0·001). Median antibody titers for serotype 2 were significantly lower for IPV than for fIPV recipients (3·0, CI95%= 3 - 3·5 vs. 4·8, CI95%= 4·5 - 5·2, p<0·001). Seroprevalence for serotypes 1 and 3 was above 90% and was not significantly different between IPV and fIPV recipients., Interpretation: Ecuador achieved significantly better poliovirus serotype 2 immunogenicity with two fIPV doses than with one IPV dose, while preserving vaccine supply and reducing costs. Our data provide further evidence that fIPV is a beneficial and potentially a cost-effective option in polio immunization., Funding: WHO obtained funds for the study from Rotary International., Competing Interests: None declared, all authors., (© 2022 World Health Organization.)

Background: Rotavirus vaccine use in national immunisation programmes has led to declines in hospital admissions for rotavirus gastroenteritis among children; however, the global impact of rotavirus vaccine introduction has not been described using primary data. We describe the impact of rotavirus vaccine introduction on admissions for acute rotavirus gastroenteritis in primarily low-income and middle-income countries, using 9 years of data from the WHO-coordinated Global Rotavirus Surveillance Network (GRSN)., Methods: Between Jan 1, 2008, and Dec 31, 2016, children younger than 5 years of age who were admitted to hospital with acute gastroenteritis were prospectively enrolled in GRSN sites. We included sites that enrolled children and collected stool specimens monthly and tested at least 100 specimens annually in the impact analysis, with a separate analysis taking into account site continuity. We compared proportions of acute gastroenteritis cases positive for rotavirus in the pre-vaccine and post-vaccine periods and calculated mean proportion changes for WHO regions, with 95% CIs; these findings were then compared with interrupted time series analyses. We did further sensitivity analyses to account for rotavirus vaccination coverage levels and sites that collected specimens for at least 11 months per year and tested at least 80 specimens per year. We also analysed the age distribution of rotavirus-positive cases before and after vaccine introduction., Findings: 403 140 children younger than 5 years of age admitted to hospital with acute gastroenteritis from 349 sites in 82 countries were enrolled over the study period, of whom 132 736 (32·9%) were positive for rotavirus. We included 305 789 children from 198 sites in 69 countries in the impact analysis. In countries that had not introduced rotavirus vaccine in their national immunisation programmes, rotavirus was detected in 38·0% (95% CI 4·8-73·4) of admissions for acute gastroenteritis annually whereas in those that have introduced the vaccine, rotavirus was detected in 23·0% (0·7-57·7) of admissions for acute gastroenteritis, showing a 39·6% (35·4-43·8) relative decline following introduction. Interrupted time series analyses confirmed these findings. Reductions by WHO regions ranged from 26·4% (15·0-37·8) in the Eastern Mediterranean Region to 55·2% (43·0-67·4) in the European Region and were sustained in nine countries (contributing up to 31 sites) for 6-10 years. The age distribution of children with rotavirus gastroenteritis shifted towards older children after rotavirus vaccine introduction., Interpretation: A significant and sustained reduction in the proportion of hospital admissions for acute gastroenteritis due to rotavirus was seen among children younger than 5 years in GRSN sites following rotavirus vaccine introduction. These findings highlight the need to incorporate rotavirus vaccines into immunisation programmes in countries that have not yet introduced them and underline the importance of high-quality surveillance., Funding: The GRSN receives funding from Gavi, the Vaccine Alliance and the US Centers for Disease Control and Prevention. No specific funding was provided for this Article., (© 2019 World Health Organization; licensee Elsevier. This is an Open Access article published under the CC BY-NC-ND 3.0 IGO license which permits users to download and share the article for non-commercial purposes, so long as the article is reproduced in the whole without changes, and provided the original source is properly cited. This article shall not be used or reproduced in association with the promotion of commercial products, services, or any entity. There should be no suggestion that WHO endorses any specific organisation, products, or services. The use of the WHO logo is not permitted. This notice should be preserved along with the article's original URL.)