Effectiveness of Monovalent mRNA Vaccines Against COVID-19-Associated Hospitalization Among Immunocompetent Adults During BA.1/BA.2 and BA.4/BA.5 Predominant Periods of SARS-CoV-2 Omicron Variant in the United States - IVY Network, 18 States, December 26, 2021-August 31, 2022.

The SARS-CoV-2 Omicron variant (B.1.1.529 or BA.1) became predominant in the United States by late December 2021 (1). BA.1 has since been replaced by emerging lineages BA.2 (including BA.2.12.1) in March 2022, followed by BA.4 and BA.5, which have accounted for a majority of SARS-CoV-2 infections since late June 2022 (1). Data on the effectiveness of monovalent mRNA COVID-19 vaccines against BA.4/BA.5-associated hospitalizations are limited, and their interpretation is complicated by waning of vaccine-induced immunity (2-5). Further, infections with earlier Omicron lineages, including BA.1 and BA.2, reduce vaccine effectiveness (VE) estimates because certain persons in the referent unvaccinated group have protection from infection-induced immunity. The IVY Network† assessed effectiveness of 2, 3, and 4 doses of monovalent mRNA vaccines compared with no vaccination against COVID-19-associated hospitalization among immunocompetent adults aged ≥18 years during December 26, 2021-August 31, 2022. During the BA.1/BA.2 period, VE 14-150 days after a second dose was 63% and decreased to 34% after 150 days. Similarly, VE 7-120 days after a third dose was 79% and decreased to 41% after 120 days. VE 7-120 days after a fourth dose was 61%. During the BA.4/BA.5 period, similar trends were observed, although CIs for VE estimates between categories of time since the last dose overlapped. VE 14-150 days and >150 days after a second dose was 83% and 37%, respectively. VE 7-120 days and >120 days after a third dose was 60%and 29%, respectively. VE 7-120 days after the fourth dose was 61%. Protection against COVID-19-associated hospitalization waned even after a third dose. The newly authorized bivalent COVID-19 vaccines include mRNA from the ancestral SARS-CoV-2 strain and from shared mRNA components between BA.4 and BA.5 lineages and are expected to be more immunogenic against BA.4/BA.5 than monovalent mRNA COVID-19 vaccines (6-8). All eligible adults aged ≥18 years§ should receive a booster dose, which currently consists of a bivalent mRNA vaccine, to maximize protection against BA.4/BA.5 and prevent COVID-19-associated hospitalization.

A newly characterized malaria antigen on erythrocyte and merozoite surfaces induces parasite inhibitory antibodies.

We previously identified a Plasmodium falciparum (Pf) protein of unknown function encoded by a single-copy gene, PF3D7_1134300, as a target of antibodies in plasma of Tanzanian children in a whole-proteome differential screen. Here we characterize this protein as a blood-stage antigen that localizes to the surface membranes of both parasitized erythrocytes and merozoites, hence its designation as Pf erythrocyte membrane and merozoite antigen 1 (PfEMMA1). Mouse anti-PfEMMA1 antisera and affinity-purified human anti-PfEMMA1 antibodies inhibited growth of P. falciparum strains by up to 68% in growth inhibition assays. Following challenge with uniformly fatal Plasmodium berghei (Pb) ANKA, up to 40% of mice immunized with recombinant PbEMMA1 self-cured, and median survival of lethally infected mice was up to 2.6-fold longer than controls (21 vs. 8 d, P = 0.005). Furthermore, high levels of naturally acquired human anti-PfEMMA1 antibodies were associated with a 46% decrease in parasitemia over 2.5 yr of follow-up of Tanzanian children. Together, these findings suggest that antibodies to PfEMMA1 mediate protection against malaria.

Prevalence and spectrum of illness among hospitalized adults with malaria in Blantyre, Malawi.

BACKGROUND: As control interventions are rolled out, the burden of malaria may shift from young children to older children and adults as acquisition of immunity is slowed and persistence of immunity is short-lived. Data for malaria disease in adults are difficult to obtain because of co-morbid conditions and because parasitaemia may be asymptomatic. Regular surveys of adult admissions to a hospital in Malawi were conducted to characterize the clinical spectrum of malaria and to establish a baseline to monitor changes that occur in future. METHODS: In 2011-2012, at Queen Elizabeth Hospital, Blantyre, four separated one-week surveys in the peak malaria transmission period (wet season) and three one-week surveys in the low transmission period (dry season) were conducted using rapid diagnostic tests (RDT) with confirmation of parasitaemia by microscopy. All adults (aged ≥15) being admitted to the adult medical wards regardless of the suspected diagnosis, were enrolled. Participants with a positive malaria test underwent a standardized physical examination and laboratory tests. Malaria syndromes were characterized by reviewing charts and laboratory results on discharge. RESULTS: 765 adult admissions were screened. 63 (8.2%) were RDT-positive with 61 (8.0%) positive by microscopy. Over the course of the seven study weeks, two patients were judged to have incidental parasitaemia, 31 (4.1%) had uncomplicated malaria and 28 (3.7%) had severe malaria. Both uncomplicated and severe malaria cases were more common in the rainy season than the dry season. Prostration (22/28 cases) and hyperparasitaemia (>250,000 parasites/µl) (9/28) were the most common features of severe malaria. Jaundice (4/28), severe anaemia (2/28), hyperlactataemia (2/28), shock (1/28) and haemoglobinuria (1/28) were less commonly seen, and no patient had severe metabolic derangement or organ failure. There were no deaths attributable to malaria. CONCLUSION: In this study of adults admitted to hospital in southern Malawi, an area with year-round transmission of Plasmodium falciparum, classical metabolic and organ complications of malaria were not encountered. Prostration and hyperparasitaemia were more common indicators of severity in patients admitted with malaria, none of whom died. These data will provide a baseline for monitoring trends in the frequency and clinical patterns of severe malaria in adults.