Antibody levels predict vaccine efficacy Symptomatic COVID-19 infection can be prevented by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines. A “correlate of protection” is a molecular biomarker to measure how much immunity is needed to fight infection and is key for successful global immunization programs. Gilbert et al . determined that antibodies are the correlate of protection in vaccinated individuals enrolled in the Moderna COVE phase 3 clinical trial (see the Perspective by Openshaw). By measuring binding and neutralizing antibodies against the viral spike protein, the authors found that the levels of both antibodies correlated with the degree of vaccine efficacy. The higher the antibody level, the greater the protection afforded by the messenger RNA (mRNA) vaccine. Antibody levels that predict mRNA vaccine efficacy can therefore be used to guide vaccine regimen modifications and support regulatory approvals for a broader spectrum of the population. —PNK

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Background Although antiretroviral therapy has the ability to fully restore a normal CD4+ cell count (>500 cells/mm3) in most patients, it is not yet clear whether all patients can achieve normalization of their CD4+ cell count, in part because no study has followed up patients for >7 years. Methods Three hundred sixty-six patients from 5 clinical cohorts who maintained a plasma human immunodeficiency virus (HIV) RNA level ≤1000 copies/mL for at least 4 years after initiation of antiretroviral therapy were included. Changes in CD4+ cell count were evaluated using mixed-effects modeling, spline-smoothing regression, and Kaplan-Meier techniques. Results The majority (83%) of the patients were men. The median CD4+ cell count at the time of therapy initiation was 201 cells/mm3 (interquartile range, 72−344 cells/mm3), and the median age was 47 years. The median follow-up period was 7.5 years (interquartile range, 5.5−9.7 years). CD4+ cell counts continued to increase throughout the follow-up period, albeit slowly after year 4. Although almost all patients (95%) who started therapy with a CD4+ cell count ≥300 cells/mm3 were able to attain a CD4+ cell count ≥500 cells/mm3, 44% of patients who started therapy with a CD4+ cell count <100 cells/mm3 and 25% of patients who started therapy with a CD4+ cell count of 100−200 cells/mm3 were unable to achieve a CD4+ cell count >500 cells/mm3 over a mean duration of follow-up of 7.5 years; many did not reach this threshold by year 10. Twenty-four percent of individuals with a CD4+ cell count <500 cells/mm3 at year 4 had evidence of a CD4+ cell count plateau after year 4. The frequency of detectable viremia (“blips”) after year 4 was not associated with the magnitude of the CD4+ cell count change. Conclusions A substantial proportion of patients who delay therapy until their CD4+ cell count decreases to <200 cells/mm3 do not achieve a normal CD4+ cell count, even after a decade of otherwise effective antiretroviral therapy. Although the majority of patients have evidence of slow increases in their CD4+ cell count over time, many do not. These individuals may have an elevated risk of non–AIDS-related morbidity and mortality.

Background Microneedle patches provide an alternative to conventional needle-and-syringe immunization, and potentially offer improved immunogenicity, simplicity, cost-effectiveness, acceptability and safety. We describe safety, immunogenicity and acceptability of the first-in-human study on single, dissolvable microneedle patch vaccination against influenza. Methods The TIV-MNP 2015 study was a phase 1, partially blinded, placebo-controlled, randomized clinical trial conducted at Emory University that enrolled non-pregnant, immunocompetent adults (age 18–49 years) from Atlanta (USA) and naïve to 2014–2015 influenza vaccine. Participants were equally randomized among four groups and received a single dose of inactivated influenza vaccine 1) by microneedle patch or 2) by intramuscular injection, or received 3) placebo by microneedle patch, all administered by an unblinded healthcare worker; or received 4) inactivated influenza vaccine by microneedle patch self-administered by study participants. Primary safety outcomes were reactogenicity, grade 3 adverse events and serious adverse events within 8, 28 and 180 days and secondary safety outcomes were new-onset chronic illnesses within 180 days and unsolicited adverse events within 28 days all analyzed by intention to treat. Secondary immunogenicity outcomes were antibody titers at day 28 as well as seroconversion and seroprotection rates all determined by hemagglutination inhibition antibody. The trial is completed and registered with ClinicalTrials.gov, NCT02438423. Findings Twenty-five participants per group were enrolled between June 23 and September 25, 2015. There were no related serious adverse events, no related grade 3 or higher adverse events and no new-onset chronic illnesses. Overall incidence of solicited and unsolicited events was similar among vaccinated groups. Reactogenicity was mild, transient and most commonly reported as tenderness at 60% (95% CI, 39– 79%) and pain at 44% (95% CI, 24–65%) after intramuscular injection and tenderness at 66% (95% CI, 51–79%), erythema at 40% (95% CI, 26–55%) and pruritus at 82% (95% CI, 69–91%) after vaccination by microneedle patch application The geometric mean titers were comparable at day 28, between the microneedle patch administered by healthcare worker and the intramuscular route with values of 1197 (95% CI, 855– 1675) and 997 (95% CI, 703–1415) (p=0.5), respectively, for the H1N1 strain; 287 (95% CI, 192–430) and 223 (95% CI, 160–312) (p=0.4), respectively, for the H3N2 strain and 126 (95% CI, 86–184) and 94 (95% CI, 73–122) (p=0.06), respectively, for the B strain. Similar GMT titers were observed in participants who self-administered the microneedle patch. The seroconversion rates were significantly higher at day 28 after microneedle patch vaccination compared to placebo and were comparable to intramuscular injection. Interpretation Use of dissolvable microneedle patches for influenza vaccination was well-tolerated and generated robust antibody responses. Funding National Institutes of Health.