An extended interval between vaccination and infection enhances hybrid immunity against SARS-CoV-2 variants.

As the COVID-19 pandemic continues, long-term immunity against SARS-CoV-2 will be important globally. Official weekly cases have not dropped below 2 million since September of 2020, and continued emergence of novel variants has created a moving target for our immune systems and public health alike. The temporal aspects of COVID-19 immunity, particularly from repeated vaccination and infection, are less well understood than short-term vaccine efficacy. In this study, we explored the effect of combined vaccination and infection, also known as hybrid immunity, and the timing thereof on the quality and quantity of antibodies elicited in a cohort of 96 health care workers. We found robust neutralizing antibody responses among those with hybrid immunity; these hybrid immune responses neutralized all variants, including BA.2. Neutralizing titers were significantly improved for those with longer vaccine-infection intervals of up to 400 days compared with those with shorter intervals. These results indicate that anti-SARS-CoV-2 antibody responses undergo continual maturation following primary exposure by either vaccination or infection for at least 400 days after last antigen exposure. We show that neutralizing antibody responses improved upon secondary boosting, with greater potency seen after extended intervals. Our findings may also extend to booster vaccine doses, a critical consideration in future vaccine campaign strategies.

Omicron neutralizing antibody response following booster vaccination compared with breakthrough infection.

BACKGROUND: The spread of the vaccine-resistant Omicron severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants threatens unvaccinated and fully vaccinated individuals, and accelerated booster vaccination campaigns are underway to mitigate the ongoing wave of Omicron cases. The immunity provided by standard vaccine regimens, boosted regimens, and immune responses elicited by vaccination plus natural infection remain incompletely understood. The magnitude, quality, and durability of serological responses, and the likelihood of protection against future SARS-CoV-2 variants following these modes of exposure, are poorly characterized but are critical to the future trajectory of the coronavirus disease 2019 (COVID-19) pandemic. METHODS: Ninety-nine individuals were semi-randomly selected from a larger vaccination cohort following vaccination and, in some cases, breakthrough infection. We analyzed spike receptor-binding domain-specific immunoglobulin G (IgG), IgA, and IgM by enzyme-linked immunosorbent assay, neutralizing antibody titers against live SARS-CoV-2 variants, and antibody-dependent cell-mediated phagocytosis. FINDINGS: In 99 vaccinated adults, compared with responses after two doses of an mRNA regimen, the immune responses 3 months after a third vaccine dose and 1 month after breakthrough infection due to prior variants show dramatic increases in magnitude, potency, and breadth, including increased antibody-dependent cellular phagocytosis and robust neutralization of the currently circulating Omicron BA.2 variant. CONCLUSIONS: Boosters and natural infection substantially boost immune responses. As the number of Omicron sub-variant cases rise and as global vaccination and booster campaigns continue, an increasing proportion of the world's population will acquire potent immune responses that may be protective against future SARS-CoV-2 variants. FUNDING: This work was funded by the M. J. Murdock Charitable Trust, the OHSU Foundation, the NIH (T32HL083808), and OHSU Innovative IDEA.

BNT162b2-induced neutralizing and non-neutralizing antibody functions against SARS-CoV-2 diminish with age.

Each severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant renews concerns about decreased vaccine neutralization weakening efficacy. However, while prevention of infection varies, protection from disease remains and implicates immunity beyond neutralization in vaccine efficacy. Polyclonal antibodies function through Fab domains that neutralize virus and Fc domains that induce non-neutralizing responses via engagement of Fc receptors on immune cells. To understand how vaccines promote protection, we leverage sera from 51 SARS-CoV-2 uninfected individuals after two doses of the BNT162b2 mRNA vaccine. We show that neutralizing activities against clinical isolates of wild-type and five SARS-CoV-2 variants, including Omicron BA.2, link to FcγRIIIa/CD16 non-neutralizing effector functions. This is associated with post-translational afucosylation and sialylation of vaccine-specific antibodies. Further, polyfunctional neutralizing and non-neutralizing breadth, magnitude, and coordination diminish with age. Thus, studying Fc functions in addition to Fab-mediated neutralization provides greater insight into vaccine efficacy for vulnerable populations, such as the elderly, against SARS-CoV-2 and novel variants.

Omicron neutralizing antibody response following booster vaccination compared with breakthrough infection

Background The spread of the vaccine-resistant Omicron SARS-CoV-2 variants threatens unvaccinated and fully vaccinated individuals, and accelerated booster vaccination campaigns are underway to mitigate the ongoing wave of Omicron cases. The immunity provided by standard vaccine regimens, boosted regimens, and immune responses elicited by vaccination plus natural infection remain incompletely understood. The magnitude, quality and durability of serological responses, and likelihood of protection against future SARS-CoV-2 variants following these modes of exposure are poorly characterized but are critical to the future trajectory of the COVID-19 pandemic. Methods Ninety-nine individuals were semi-randomly selected from a larger vaccination cohort following vaccination and in some cases breakthrough infection. We analyzed spike receptor-binding domain-specific IgG, IgA, and IgM by enzyme-linked immunosorbent assay, neutralizing antibody titers against live SARS-CoV-2 variants, and antibody-depended cell-mediated phagocytosis. Findings In 99 vaccinated adults, compared with responses after two doses of an mRNA regimen, the immune responses three months after a third vaccine dose and one month after breakthrough infection due to prior variants show dramatic increases in magnitude, potency, and breadth, including increased antibody dependent cellular phagocytosis and robust neutralization of the currently circulating Omicron BA.2 variant. Conclusions Boosters and natural infection substantially boost immune responses. As the number of Omicron subvariant cases rise and as global vaccination and booster campaigns continue, an increasing proportion of the world’s population will acquire potent immune responses that may be protective against future SARS-CoV-2 variants. Graphical The nature of immune responses following 2-dose, 3–dose vaccination and breakthrough infection remains to be fully investigated. Curlin et al show that boosted vaccine regimens and breakthrough infection enhance immune responses similarly, but there is a progressive loss of efficacy against newly emerging variants.

BNT162b2 induced neutralizing and non-neutralizing antibody functions against SARS-CoV-2 diminish with age

Each SARS-CoV-2 variant renews concerns about decreased vaccine neutralization weakening efficacy. However, while prevention of infection varies, protection from disease remains and implicates immunity beyond neutralization in vaccine efficacy. Polyclonal antibodies function through Fab domains that neutralize virus, and Fc domains that induce non-neutralizing responses via engagement of Fc receptors on immune cells. To understand how vaccines promote protection, we leverage sera from 51 SARS-CoV-2 uninfected individuals after two doses of the BNT162b2 mRNA vaccine. We show neutralizing activities against clinical isolates of wildtype and five SARS-CoV-2 variants, including Omicron BA.2, link to FcγRIIIa/CD16 non-neutralizing effector functions. This is associated with post-translational afucosylation and sialylation of vaccine specific antibodies. Further, polyfunctional neutralizing and non-neutralizing breadth, magnitude and coordination diminish with age. Thus, studying Fc functions in addition to Fab mediated neutralization provides greater insight into vaccine efficacy for vulnerable populations such as the elderly against SARS-CoV-2 and novel variants. Graphical Bates et al. investigate viral neutralization, antibody glycosylation and Fc-mediated effector functions from BNT162b2. Neutralization and antibody-dependent natural killer cell activation correlate. Vaccine-specific IgG display distinct glycosylation patterns with afucosylation and sialylation associating with natural killer cell activation. These antibody properties collectively diminish in those ≥65 years old.

Bimodal distribution pattern associated with the PCR cycle threshold (Ct) and implications in COVID-19 infections.

SARS-CoV-2 is notable for its extremely high level of viral replication in respiratory epithelial cells, relative to other cell types. This may partially explain the high transmissibility and rapid global dissemination observed during the COVID-19 pandemic. Polymerase chain reaction (PCR) cycle threshold (Ct) number has been widely used as a proxy for viral load based on the inverse relationship between Ct number and amplifiable genome copies present in a sample. We examined two PCR platforms (Centers for Disease Control and Prevention 2019-nCoV Real-time RT-PCR, Integrated DNA Technologies; and TaqPath COVID-19 multi-plex combination kit, ThermoFisher Scientific) for their performance characteristics and Ct distribution patterns based on results generated from 208,947 clinical samples obtained between October 2020 and September 2021. From 14,231 positive tests, Ct values ranged from 8 to 39 and displayed a pronounced bimodal distribution. The bimodal distribution persisted when stratified by gender, age, and time period of sample collection during which different viral variants circulated. This finding may be a result of heterogeneity in disease progression or host response to infection irrespective of age, gender, or viral variants. Quantification of respiratory mucosal viral load may provide additional insight into transmission and clinical indicators helpful for infection control.

Neonatal Multisystem Inflammatory Syndrome (MIS-N): The First Case Report in Thailand

Cases of multisystem inflammatory syndrome in children (MIS-C-like disease), have rarely been reported in neonates. A 33-week gestational age twin B female neonate presented with respiratory distress, tachycardia, and abdominal distention at 15 days of age. Echocardiogram found reduced left ventricular ejection fraction to 33%. Cardiac enzyme levels were all elevated: creatine kinase-MB 6.1 ng/mL (normal 0–4.5 ng/mL), troponin-T 170 ng/L (normal < 14 ng/L) and NT-proBNP > 35,000 pg/mL (normal 250.0 to 3987.0 pg/mL). Multiplex PCR of nasopharyngeal swab material was negative for respiratory pathogens. Serological tests revealed negative anti-spike SARS-CoV-2 IgM but positive anti-nucleocapsid SARS-CoV-2 IgG in both the mother and the patient. The mother provided a history of COVID-19 during pregnancy at 19 weeks gestation. The patient was diagnosed with neonatal multisystem inflammatory syndrome (MIS-N) and successfully treated with intravenous immunoglobulin (two doses of 1 gm/kg/dose) and methylprednisolone (2 mg/kg/day for 5 days then tapered off). She later developed coronary vessel (LMCA and RCA) dilation. The non-identical twin A did not develop MIS-N, suggesting a role of host genetic background. Newborn infants born to SARS-CoV-2-infected mothers at any time during pregnancy should be closely monitored for MIS-N. The optimal treatment approaches to this syndrome and the prognosis require further study.

Vaccination before or after SARS-CoV-2 infection leads to robust humoral response and antibodies that effectively neutralize variants.

Current coronavirus disease 2019 (COVID-19) vaccines effectively reduce overall morbidity and mortality and are vitally important to controlling the pandemic. Individuals who previously recovered from COVID-19 have enhanced immune responses after vaccination (hybrid immunity) compared with their naïve-vaccinated peers; however, the effects of post-vaccination breakthrough infections on humoral immune response remain to be determined. Here, we measure neutralizing antibody responses from 104 vaccinated individuals, including those with breakthrough infections, hybrid immunity, and no infection history. We find that human immune sera after breakthrough infection and vaccination after natural infection broadly neutralize SARS-CoV-2 (severe acute respiratory coronavirus 2) variants to a similar degree. Although age negatively correlates with antibody response after vaccination alone, no correlation with age was found in breakthrough or hybrid immune groups. Together, our data suggest that the additional antigen exposure from natural infection substantially boosts the quantity, quality, and breadth of humoral immune response regardless of whether it occurs before or after vaccination.

Neutralization of SARS-CoV-2 variants by convalescent and BNT162b2 vaccinated serum.

SARS-CoV-2 and its variants continue to infect hundreds of thousands every day despite the rollout of effective vaccines. Therefore, it is essential to understand the levels of protection that these vaccines provide in the face of emerging variants. Here, we report two demographically balanced cohorts of BNT162b2 vaccine recipients and COVID-19 patients, from which we evaluate neutralizing antibody titers against SARS-CoV-2 as well as the B.1.1.7 (alpha) and B.1.351 (beta) variants. We show that both B.1.1.7 and B.1.351 are less well neutralized by serum from vaccinated individuals, and that B.1.351, but not B.1.1.7, is less well neutralized by convalescent serum. We also find that the levels of variant-specific anti-spike antibodies are proportional to neutralizing activities. Together, our results demonstrate the escape of the emerging SARS-CoV-2 variants from neutralization by serum antibodies, which may lead to reduced protection from re-infection or increased risk of vaccine breakthrough.