Immunogenicity and safety of NVX-CoV2373 as a booster: A phase 3 randomized clinical trial in adults

BACKGROUND

To combat the SARS-CoV-2 pandemic, multiple vaccines using different manufacturing platforms have been developed, including NVX-CoV2373 (an adjuvanted recombinant protein vaccine). As SARS-CoV-2 variants have emerged, some of which evade vaccine-induced immunity, introduction of vaccine booster doses has become critical. Employing different vaccine types for primary series vaccination and boosting could expand vaccine coverage and access. This study assessed whether NVX-CoV2373 would induce robust responses when used as a booster.

METHODS

The 2019nCoV-307 study was a phase 3, randomized, observer-blinded trial evaluating immunogenicity and safety of NVX-CoV2373 in previously vaccinated adults aged 18-49 years in the United States (NCT05463068). Participants were randomized 1:1:1 to receive one intramuscular injection of NVX-CoV2373 from one of three different manufacturing lots. Immunogenicity was assessed by immunoglobulin G (IgG) and neutralizing antibodies (NAb). These responses were compared for the three lots, and for participants with primary series with or without a prior booster dose of the mRNA-1273, BNT162b2, Ad26.COV2.S, or NVX-CoV2373 COVID-19 vaccines.

RESULTS

A total of 911 participants were randomized between July 11 and 13, 2022, with 905 being assessed for safety and 848 for immunogenicity. Immunogenicity of NVX-CoV2373 met prespecified equivalence criteria between lots, and the booster dose was well-tolerated. NVX-CoV2373 induced robust IgG and NAb responses when used as a first or later booster dose, regardless of primary series vaccine type. Seroconversion rates were also similar across previous vaccine types. Induced antibodies were strongly reactive, even to the immune-evasive Omicron BA.1 and BA.5 variants.

CONCLUSIONS

NVX-CoV2373 showed consistent immunogenicity between lots, with no new safety signals identified. Use of NVX-CoV2373 as a booster dose (first or later) is supported.

Induction of Cross-reactive Hemagglutination Inhibiting Antibody and Polyfunctional CD4+ T-cell Responses by a Recombinant Matrix-M-Adjuvanted Hemagglutinin Nanoparticle Influenza Vaccine

Background

Recurrent reports of suboptimal influenza vaccine effectiveness have renewed calls to develop improved, broadly cross-protective influenza vaccines. Here, we evaluated the safety and immunogenicity of a novel, saponin (Matrix-M)–adjuvanted, recombinant hemagglutinin (HA) quadrivalent nanoparticle influenza vaccine (qNIV).

Methods

We conducted a randomized, observer-blind, comparator-controlled (trivalent high-dose inactivated influenza vaccine [IIV3-HD] or quadrivalent recombinant influenza vaccine [RIV4]), safety and immunogenicity trial of qNIV (5 doses/formulations) in healthy adults ≥65 years. Vaccine immunogenicity was measured by hemagglutination-inhibition assays using reagents that express wild-type hemagglutination inhibition (wt-HAI) sequences and cell-mediated immune responses.

Results

A total of 1375 participants were randomized, immunized, and followed for safety and immunogenicity. Matrix-M–adjuvanted qNIV induced superior wt-HAI antibody responses against 5 of 6 homologous or drifted strains compared with unadjuvanted qNIV. Adjuvanted qNIV induced post-vaccination wt-HAI antibody responses at day 28 that were statistically higher than IIV3-HD against a panel of homologous or drifted A/H3N2 strains, similar to IIV3-HD against homologous A/H1N1 and B (Victoria) strains and similar to RIV4 against all homologous and drifted strains evaluated. The qNIV formulation with 75 µg Matrix-M adjuvant induced substantially higher post-vaccination geometric mean fold increases of influenza HA-specific polyfunctional CD4+ T cells compared with IIV3-HD or RIV4. Overall, similar frequencies of solicited and unsolicited adverse events were reported in all treatment groups.

Conclusions

qNIV with 75 µg Matrix-M adjuvant was well tolerated and induced robust antibody and cellular responses, notably against both homologous and drifted A/H3N2 viruses. Further investigation in a pivotal phase 3 trial is underway.

Clinical Trials Registration

NCT03658629.

LB19. Progress Toward a Vaccine for Maternal Immunization to Prevent Respiratory Syncytial Virus (RSV) Lower Respiratory Tract Illness (LRTI) in Infants

Background

RSV is the leading cause of infant LRTI and hospitalization worldwide. The greatest burden of severe disease is in term infants <5 months old. Novavax is developing an aluminum-adjuvanted RSV F nanoparticle vaccine for use in the third trimester of pregnancy, with the goal of preventing medically significant infant RSV LRTI in the first 3–6 months of life via transplacental transfer of maternal antibodies.

Method

After dose-finding studies in 1,050 women, we studied vaccine safety and immunogenicity in a Phase 2 trial in 50 healthy third trimester pregnant women. Safety was assessed in mothers and infants, focusing on pregnancy and peri-partum outcomes. We measured binding and functional RSV antibodies in mothers at baseline, day 14, delivery, and days 35 and 180 post-partum, in cord blood, and in infant sera on days 14, 35, 60, and 180 of life. Anti-F antibody specificities were probed with biolayer interferometry and monoclonal antibodies (mabs) to known epitopes.

Result

In Phase 2, RSV F nanoparticle vaccine was immunogenic, safe, and well-tolerated in pregnant women. Anti-F IgG and neutralizing antibodies were elicited. Increases in antibodies competitive with mabs to neutralizing epitope sites Ø, VIII, II, and IV, and also the p27 domain displayed by the pre-fusogenic F protein, were present in maternal and infant sera of vaccinated subject pairs. Transplacental transfer of RSV antibodies was more efficient (110 to 120%) in women immunized >30 days before delivery compared with those vaccinated later; RSV antibody t_1/2 ranged from 30 to 41 days in infants. We have subsequently enrolled 4,636 pregnant women and their infants in a global observer-blind, randomized, placebo-controlled Phase 3 trial assessing efficacy against medically significant RSV LRTI. In November 2017, an informational analysis performed by an independent statistician, the sponsor remaining blinded, yielded a posterior probability of ≥90% that efficacy was >0%.

Conclusion

RSV F nanoparticle vaccine is immunogenic in pregnancy, and neutralizing antibodies, including those competing for pre-and post-fusion F epitopes, are transferred efficiently transplacentally. An analysis of Phase 3 efficacy against medically signifcant infant RSV LRTI is projected for Q1, 2019.

Disclosures

L. Fries, Novavax: Employee and Shareholder, Salary. D. N. Thomas, Novavax: Employee, Salary. G. Smith, Novavax: Employee and Shareholder, Salary. J. Plested, Novavax: Employee, Salary. P. Piedra, Novavax: Collaborator, Consultant, Research Contractor and Scientific Advisor, Consulting fee, contract fees for immunologic assays and Research support. N. Patel, Novavax: Employee and Shareholder, Salary. I. Cho, Novavax: Employee and Shareholder, Salary. G. Glenn, Novavax: Employee and Shareholder, Salary.

The class A macrophage scavenger receptor is a major pattern recognition receptor for Neisseria meningitidis which is independent of lipopolysaccharide and not required for secretory responses

Macrophages (Mphi) play a key role in the pathogenesis of invasive meningococcal infections. The roles of two pattern recognition molecules, the Mphi scavenger receptor (SR-A) and Toll-like receptor 4 (TLR-4), have been investigated using bone marrow culture-derived Mphi (BMMphi). Surprisingly, a comparison of BMMphi from wild-type and SR-A knockout (SR-A(-/-)) mice showed that nonopsonic phagocytosis of meningococci was mediated almost exclusively via SR-A. Previous studies have demonstrated only a partial involvement of the receptor in the uptake of other bacteria, such as Escherichia coli. Interestingly, we also show that lipopolysaccharide (LPS) was not the ligand for the receptor on these organisms. Further study of the downstream events of SR-A-mediated ingestion of Neisseria meningitidis demonstrated that SR-A was not required for cytokine production. To determine the bacterial and host factors required to stimulate Mphi activation, we examined TLR-4-deficient Mphi from C3H/HeJ mice and LPS-deficient meningococci. TLR-4-deficient cells elaborated reduced amounts of tumor necrosis factor alpha, interleukin-12 (IL-12), and IL-10, even though ingestion via SR-A was unaffected in these cells. Similarly, although there was no change in SR-A-mediated ingestion of LPS-deficient meningococci, the mutant failed to stimulate a Mphi-dependent cytokine response. Thus, we show that Mphi SR-A mediates opsonin-independent uptake of N. meningitidis independently of lipid A and that this activity is uncoupled from the Mphi secretion of proinflammatory cytokines, which provides a basis for further investigation of the role of this receptor in meningococcal disease in humans.

Genetic linkage analysis to identify a gene required for the addition of phosphoethanolamine to meningococcal lipopolysaccharide

Lipopolysaccharide (LPS) is important for the virulence of Neisseria meningitidis, and is the target of immune responses. We took advantage of a monoclonal antibody (Mab B5) that recognises phosphoethanolamine (PEtn) attached to the inner core of meningococcal LPS to identify genes required for the addition of PEtn to LPS. Insertional mutants that lost Mab B5 reactivity were isolated and characterised, but failed to yield genes directly responsible for PEtn substitution. Subsequent genetic linkage analysis was used to define a region of DNA containing a single intact open reading frame which is sufficient to confer B5 reactivity to a B5 negative meningococcal isolate. The results provide an initial characterisation of the genetic basis of a key, immunodominant epitope of meningococcal LPS.