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Sci Transl Med ; 15(683): eade6023, 2023 02 15.
Article in English | MEDLINE | ID: covidwho-2240695


The emergence of the SARS-CoV-2 Omicron sublineages resulted in increased transmission rates and reduced protection from vaccines. To counteract these effects, multiple booster strategies were used in different countries, although data comparing their efficiency in improving protective immunity remain sparse, especially among vulnerable populations, including older adults. The inactivated CoronaVac vaccine was among the most widely distributed vaccine worldwide and was essential in the early control of SARS-CoV-2-related hospitalizations and deaths. However, it is not well understood whether homologous versus heterologous booster doses in those fully vaccinated with CoronaVac induce distinct humoral responses or whether these responses vary across age groups. We analyzed plasma antibody responses from CoronaVac-vaccinated younger or older individuals who received a homologous CoronaVac or heterologous BNT162b2 or ChAdOx1 booster vaccine. All three evaluated boosters resulted in increased virus-specific IgG titers 28 days after the booster dose. However, we found that both IgG titers against SARS-CoV-2 Spike or RBD and neutralization titers against Omicron sublineages were substantially reduced in participants who received homologous CoronaVac compared with the heterologous BNT162b2 or ChAdOx1 booster. This effect was specifically prominent in recipients >50 years of age. In this group, the CoronaVac booster induced low virus-specific IgG titers and failed to elevate neutralization titers against any Omicron sublineage. Our results point to the notable inefficiency of CoronaVac immunization and boosting in mounting protective antiviral humoral immunity, particularly among older adults, during the Omicron wave. These observations also point to benefits of heterologous regimens in high-risk populations fully vaccinated with CoronaVac.

Antibody Formation , COVID-19 , Humans , Aged , BNT162 Vaccine , SARS-CoV-2 , Immunoglobulin G , Antibodies, Viral
Cell reports Medicine ; 2023.
Article in English | EuropePMC | ID: covidwho-2228680


The chronic infection hypothesis for novel SARS-CoV-2 variant emergence is increasingly gaining credence following the appearance of Omicron. Here we investigate intrahost evolution and genetic diversity of lineage B.1.517 during a SARS-CoV-2 chronic infection lasting for 471 days (and still ongoing) with consistently recovered infectious virus and high viral genome copies. During the infection, we find an accelerated virus evolutionary rate translating to 35 nucleotide substitutions per year, approximately two-fold higher than the global SARS-CoV-2 evolutionary rate. This intrahost evolution result in the emergence and persistence of at least three genetically distinct genotypes suggesting the establishment of spatially structured viral populations continually reseeding different genotypes into the nasopharynx. Finally, we track the temporal dynamics of genetic diversity to identify advantageous mutations and highlight hallmark changes for chronic infection. Our findings demonstrate that untreated chronic infections accelerate SARS-CoV-2 evolution, providing an opportunity for the emergence of genetically divergent variants. Graphical To understand the intrahost evolution of SARS-CoV-2 from a single patient chronically infected for at least 471 days, Chaguza et al. use whole genome sequencing to estimate the evolutionary rate, the genetic divergence of viral lineages, relative mutation rates, and frequency of mutational variants during the course of the infection.

Emerg Infect Dis ; 28(12): 2455-2462, 2022 Dec.
Article in English | MEDLINE | ID: covidwho-2141584


We evaluated daily rapid antigen test (RAT) data from 323 COVID-19-positive university students in Connecticut, USA, during an Omicron-dominant period. Day 5 positivity was 47% for twice-weekly screeners and 26%-28% for less-frequent screeners, approximately halving each subsequent day. Testing negative >10 days before diagnosis (event time ratio (ETR) 0.85 [95% CI 0.75-0.96]) and prior infection >90 days (ETR 0.50 [95% CI 0.33-0.76]) were significantly associated with shorter RAT positivity duration. Symptoms before or at diagnosis (ETR 1.13 [95% CI 1.02-1.25]) and receipt of 3 vaccine doses (ETR 1.20 [95% CI 1.04-1.39]) were significantly associated with prolonged positivity. Exit RATs enabled 53%-74% of students to leave isolation early when they began isolation at the time of the first positive test, but 15%-22% remained positive beyond the recommended isolation period. Factors associated with RAT positivity duration should be further explored to determine relationships with infection duration.

COVID-19 , Vaccines , Humans , Universities , Policy , Students