Safety, immunogenicity and antibody persistence of a bivalent Beta-containing booster vaccine against COVID-19: a phase 2/3 trial

Intranasal SARS-CoV-2 Omicron variant vaccines elicit humoral and cellular mucosal immunity in female mice

BACKGROUND

In order to prevent the emergence and spread of future variants of concern of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), developing vaccines capable of stopping transmission is crucial. The SARS-CoV-2 vaccine NDV-HXP-S can be administered live intranasally (IN) and thus induce protective immunity in the upper respiratory tract. The vaccine is based on Newcastle disease virus (NDV) expressing a stabilised SARS-CoV-2 spike protein. NDV-HXP-S can be produced as influenza virus vaccine at low cost in embryonated chicken eggs.

METHODS

The NDV-HXP-S vaccine was genetically engineered to match the Omicron variants of concern (VOC) BA.1 and BA.5 and tested as an IN two or three dose vaccination regimen in female mice. Furthermore, female mice intramuscularly (IM) vaccinated with mRNA-lipid nanoparticles (LNPs) were IN boosted with NDV-HXP-S. Systemic humoral immunity, memory T cell responses in the lungs and spleens as well as immunoglobulin A (IgA) responses in distinct mucosal tissues were characterised.

FINDINGS

NDV-HXP-S Omicron variant vaccines elicited high mucosal IgA and serum IgG titers against respective SARS-CoV-2 VOC in female mice following IN administration and protected against challenge from matched variants. Additionally, antigen-specific memory B cells and local T cell responses in the lungs were induced. Host immunity against the NDV vector did not interfere with boosting. Intramuscular vaccination with mRNA-LNPs was enhanced by IN NDV-HXP-S boosting resulting in improvement of serum neutralization titers and induction of mucosal immunity.

INTERPRETATION

We demonstrate that NDV-HXP-S Omicron variant vaccines utilised for primary immunizations or boosting efficiently elicit humoral and cellular immunity. The described induction of systemic and mucosal immunity has the potential to reduce infection and transmission.

FUNDING

This work was partially funded by the NIAIDCenters of Excellence for Influenza Research and Response (CEIRR) and by the NIAID Collaborative Vaccine Innovation Centers and by institutional funding from the Icahn School of Medicine at Mount Sinai. See under Acknowledgements for details.

Immunogenicity and safety of a recombinant Omicron BA.4/5-Delta COVID-19 vaccine ZF2202-A in Chinese adults

BACKGROUND

The Recombinant Omicron BA.4/5-Delta COVID-19 Vaccine (ZF2202-A) is primarily designed for the Delta and Omicron BA.4/5 variants. Our objective was to assess the safety and immunogenicity of ZF2202-A in Chinese adults.

METHODS

A total of 450 participants aged ≥ 18 years, who had completed primary or booster vaccination with a COVID-19 vaccine more than 6 months prior, were enrolled in this randomized, double-blind, active-controlled trial. Participants in the study and control groups were administered one dose of ZF2202-A and ZF2001, respectively. Immunogenicity subgroups were established in each group.

RESULTS

At 14 days after vaccination, the seroconversion rates of Omicron BA.4/5, BF.7, and XBB.1 in the ZF2022-A group were 67.7 %, 58.6 %, and 62.6 %, with geometric mean titers (GMTs) of neutralizing antibodies at 350.2, 491.8, and 49.5, respectively. The main adverse reactions (ARs) were vaccination site pain, pruritus, fatigue, and asthenia in both the ZF2022-A group and ZF2001 group.

CONCLUSIONS

The novel bivalent vaccine ZF2202-A demonstrated satisfactory immunogenicity and safety against Omicron variants as booster dose in adults with prior vaccination of COVID-19 vaccines.

SARS-CoV-2 Neutralization Assays Used in Clinical Trials: A Narrative Review

Since the emergence of COVID-19, extensive research efforts have been undertaken to accelerate the development of multiple types of vaccines to combat the pandemic. These include inactivated, recombinant subunit, viral vector, and nucleic acid vaccines. In the development of these diverse vaccines, appropriate methods to assess vaccine immunogenicity are essential in both preclinical and clinical studies. Among the biomarkers used in vaccine evaluation, the neutralizing antibody level serves as a pivotal indicator for assessing vaccine efficacy. Neutralizing antibody detection methods can mainly be classified into three types: the conventional virus neutralization test, pseudovirus neutralization test, and surrogate virus neutralization test. Importantly, standardization of these assays is critical for their application to yield results that are comparable across different laboratories. The development and use of international or regional standards would facilitate assay standardization and facilitate comparisons of the immune responses induced by different vaccines. In this comprehensive review, we discuss the principles, advantages, limitations, and application of different SARS-CoV-2 neutralization assays in vaccine clinical trials. This will provide guidance for the development and evaluation of COVID-19 vaccines.

Immunogenicity and Safety of SARS-CoV-2 Protein Subunit Recombinant Vaccine (IndoVac®) as a Booster Dose against COVID-19 in Indonesian Adults

According to the WHO target product profile for COVID-19 vaccines, the vaccine in development should be indicated for active immunisation in all populations. Therefore, PT Bio Farma developed a candidate vaccine in a subunit protein recombinant platform to help overcome the issue. This trial was an observer-blind, randomised, prospective intervention study. This study targeted individuals who had received complete primary doses of the authorised/approved COVID-19 vaccine. The groups were divided into the primary inactivated vaccine (CoronaVac®) group, the primary viral vector vaccine (ChAdOx1) group, and the primary mRNA vaccine (BNT162b2) group that received the recombinant protein (IndoVac®). The groups were compared with the control and primary mRNA vaccine (BNT162b2). The participants enrolled in the study were from two primary care centres in Bandung City and three primary care centres in Denpasar City. A total of 696 participants were enrolled from 1 September to 31 October 2022. The demographic characteristics of the all-vaccine group showed a uniform distribution. The results showed that, compared with the control, the investigational product had inferior effectiveness 14 days after the booster dose was administered. However, 28 days after the booster dose, the investigational product exhibited non-inferior effectiveness compared with the primary groups that received CoronaVac® (GMR 0.76 (0.57-0.99)) and ChAdOx1 (GMR 0.72 (0.56-59.93)), but the BNT162b2 group (GMR 0.61 (0.39-0.94)) was inferior to the control. At 12 months follow-up after the booster dose, three serious adverse events (SAEs) were reported in three participants, with causality not correlated with the investigated products. Neither AEs of special interest nor severe COVID-19 cases were reported throughout the follow-up period; thus, the IndoVac® vaccine as a booster was immunogenic and safe. Until the 6-month follow-up after the booster dose, the IndoVac® vaccine was well tolerated and all reported AEs resolved. This vaccine is registered and can be included in the immunisation programme.

Immune imprinting of SARS-CoV-2 responses: changing first immune impressions

Since the emergence of the ancestral severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus and the successful rollout of protective vaccines based on this original strain, SARS-CoV-2 has evolved into several variants, in a classical virus-host arms race typical of RNA viruses, to progressively evade the host immune response. Next-generation bivalent vaccines have been developed with broader protection against emerging variants than the ancestral vaccine. Nonetheless, even these vaccines show lower protection against the latest Omicron variants. Immune printing describes how an immune response to an immunogen is impacted by earlier exposures to a related immunogen. Several lessons about the effect of immune imprinting on responses to SARS-CoV-2 infection and vaccination, including age-associated impacts, can be learned from influenza. Understanding the mechanisms of imprinting of SARS-CoV-2 will be important to inform the design of vaccines that produce broader and more durable protective immune responses to emerging variants.

Assembling the RNA therapeutics toolbox

From the approval of COVID-19 mRNA vaccines to the 2023 Nobel Prize awarded for nucleoside base modifications, RNA therapeutics have entered the spotlight and are transforming drug development. While the term "RNA therapeutics" has been used in various contexts, this review focuses on treatments that utilize RNA as a component or target RNA for therapeutic effects. We summarize the latest advances in RNA-targeting tools and RNA-based technologies, including but not limited to mRNA, antisense oligos, siRNAs, small molecules and RNA editors. We focus on the mechanisms of current FDA-approved therapeutics but also provide a discussion on the upcoming workforces. The clinical utility of RNA-based therapeutics is enabled not only by the advances in RNA technologies but in conjunction with the significant improvements in chemical modifications and delivery platforms, which are also briefly discussed in the review. We summarize the latest RNA therapeutics based on their mechanisms and therapeutic effects, which include expressing proteins for vaccination and protein replacement therapies, degrading deleterious RNA, modulating transcription and translation efficiency, targeting noncoding RNAs, binding and modulating protein activity and editing RNA sequences and modifications. This review emphasizes the concept of an RNA therapeutic toolbox, pinpointing the readers to all the tools available for their desired research and clinical goals. As the field advances, the catalog of RNA therapeutic tools continues to grow, further allowing researchers to combine appropriate RNA technologies with suitable chemical modifications and delivery platforms to develop therapeutics tailored to their specific clinical challenges.

Therapeutic development targeting host heparan sulfate proteoglycan in SARS-CoV-2 infection

The global pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to an urgent need for effective therapeutic options. SARS-CoV-2 is a novel coronavirus responsible for the COVID-19 pandemic that has resulted in significant morbidity and mortality worldwide. The virus is known to enter host cells by binding to the angiotensin-converting enzyme 2 (ACE2) receptor, and emerging evidence suggests that heparan sulfate proteoglycans (HSPGs) play a crucial role in facilitating this process. HSPGs are abundant cell surface proteoglycan present in many tissues, including the lung, and have been shown to interact directly with the spike protein of SARS-CoV-2. This review aims to summarize the current understanding of the role of HSPGs in SARS-CoV-2 infection and the potential of developing new therapies targeting HSPGs.

Profiling antibody epitopes induced by mRNA-1273 vaccination and boosters

Background

Characterizing the antibody epitope profiles of messenger RNA (mRNA)-based vaccines against SARS-CoV-2 can aid in elucidating the mechanisms underlying the antibody-mediated immune responses elicited by these vaccines.

Methods

This study investigated the distinct antibody epitopes toward the SARS-CoV-2 spike (S) protein targeted after a two-dose primary series of mRNA-1273 followed by a booster dose of mRNA-1273 or a variant-updated vaccine among serum samples from clinical trial adult participants.

Results

Multiple S-specific epitopes were targeted after primary vaccination; while signal decreased over time, a booster dose after >6 months largely revived waning antibody signals. Epitope identity also changed after booster vaccination in some subjects, with four new S-specific epitopes detected with stronger signals after boosting than with primary vaccination. Notably, the strength of antibody responses after booster vaccination differed by the exact vaccine formulation, with variant-updated mRNA-1273.211 and mRNA-1273.617.2 booster formulations inducing significantly stronger S-specific signals than a mRNA-1273 booster.

Conclusion

Overall, these results identify key S-specific epitopes targeted by antibodies induced by mRNA-1273 primary and variant-updated booster vaccination.

mRNA vaccine trafficking and resulting protein expression after intramuscular administration

The mRNA vaccine route from injection site to critical immunologic tissues, as well as the localization of protein antigen following intramuscular (i.m.) administration, is crucial to generating an effective immune response. Here, we quantified mRNA at the injection site, lymph nodes, and in select tissues. mRNA was primarily present 24 h after administration and then rapidly degraded from local and systemic tissues. Histological analyses of mRNA and expressed protein at the site of administration and in the lymph nodes following i.m. administration of our vaccine in rodents and nonhuman primates (NHPs) were completed, and mRNA and protein expression were detected in tissue resident and infiltrating immune cells at the injection site. In addition, high levels of protein expression were observed within subcapsular and medullary sinus macrophages in draining lymph nodes. More important, results were similar between rodents and NHPs, indicating cross-species similarities.

Immunogenicity of an adenovirus-vectored bivalent vaccine against wild type SARS-CoV-2 and Omicron variants in a murine model

BACKGROUND

The emergence and rapid spread of new mutant strains of SARS-CoV-2 necessitate the development of a new generation vaccine capable of neutralizing a broad range of variants. When the SARS-CoV-2 Omicron variant emerged, individuals in China had already received an inactivated (INA) or a type 5 adenovirus-vectored (Ad5) SARS-CoV-2 vaccine targeting the wild-type virus. We have recently developed a bivalent recombinant type 5 vaccine targeting both the wild-type strain and the Omicron variant (Ad5-nCoV/O). The objectives of this study were to assess the immunogenicity of the bivalent vaccine as a booster against both the wild type and the Omicron variant.

METHODS

In the single immunization model, mice received one intramuscular immunization with monovalent or bivalent Ad5-vectored vaccines targeting both wild-type SARS-CoV-2 and Omicron variants. In the prime-boost model, mice were primed intramuscularly with an INA or Ad5-vectored vaccine targeting wild-type SARS-CoV-2, and then boosted intramuscularly or intranasally with heterologous or homologous INA or monovalent or bivalent Ad5-vectored vaccines targeting both wild-type SARS-CoV-2 and Omicron variants. The vaccine-induced antibody responses and cellular immune responses were measured using ELISA, pseudovirus-based neutralization assays, the intracellular cytokine staining (ICS) and ELISpot.

RESULTS

Single-dose prime vaccination with the monovalent and bivalent vaccines elicited robust antibody responses and CD4 + and CD8 + cellular responses against the spike protein of WT and Omicron SARS-CoV-2. Both intramuscular and intranasal boost vaccination with the bivalent Ad5-nCoV/O following a prime with INA or Ad5-vectored vaccines induced strong serum neutralization antibody responses to both wild type and Omicron variants. A heterologous prime-boost vaccination elicited greater neutralization antibody responses than a homologous prime-boost vaccination when mice were boosted with Ad5-vectored vaccines following a prime with INA. Intranasal boost also resulted in significant mucosal IgA responses.

CONCLUSION

The bivalent vaccine Ad5-nCoV/O exhibited robust immunogenicity, inducing broad-spectrum cross-neutralizing antibodies and cellular immune responses against both wild type and Omicron variants of SARS-CoV-2. The results demonstrated the potential of the bivalent vaccine in addressing the challenges posed by emerging SARS-CoV-2 Omicron variants.

A Gamma-adapted subunit vaccine induces broadly neutralizing antibodies against SARS-CoV-2 variants and protects mice from infection

In the context of continuous emergence of SARS-CoV-2 variants of concern (VOCs), one strategy to prevent the severe outcomes of COVID-19 is developing safe and effective broad-spectrum vaccines. Here, we present preclinical studies of a RBD vaccine derived from the Gamma SARS-CoV-2 variant adjuvanted with Alum. The Gamma-adapted RBD vaccine is more immunogenic than the Ancestral RBD vaccine in terms of inducing broader neutralizing antibodies. The Gamma RBD presents more immunogenic B-cell restricted epitopes and induces a higher proportion of specific-B cells and plasmablasts than the Ancestral RBD version. The Gamma-adapted vaccine induces antigen specific T cell immune responses and confers protection against Ancestral and Omicron BA.5 SARS-CoV-2 challenge in mice. Moreover, the Gamma RBD vaccine induces higher and broader neutralizing antibody activity than homologous booster vaccination in mice previously primed with different SARS-CoV-2 vaccine platforms. Our study indicates that the adjuvanted Gamma RBD vaccine is highly immunogenic and a broad-spectrum vaccine candidate.

Challenges in Emerging Vaccines and Future Promising Candidates against SARS-CoV-2 Variants

Since the COVID-19 outbreak, the severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) virus has evolved into variants with varied infectivity. Vaccines developed against COVID-19 infection have boosted immunity, but there is still uncertainty on how long the immunity from natural infection or vaccination will last. The present study attempts to outline the present level of information about the contagiousness and spread of SARS-CoV-2 variants of interest and variants of concern (VOCs). The keywords like COVID-19 vaccine types, VOCs, universal vaccines, bivalent, and other relevant terms were searched in NCBI, Science Direct, and WHO databases to review the published literature. The review provides an integrative discussion on the current state of knowledge on the type of vaccines developed against SARS-CoV-2, the safety and efficacy of COVID-19 vaccines concerning the VOCs, and prospects of novel universal, chimeric, and bivalent mRNA vaccines efficacy to fend off existing variants and other emerging coronaviruses. Genomic variation can be quite significant, as seen by the notable differences in impact, transmission rate, morbidity, and death during several human coronavirus outbreaks. Therefore, understanding the amount and characteristics of coronavirus genetic diversity in historical and contemporary strains can help researchers get an edge over upcoming variants.

Three immunizations with Novavax's protein vaccines increase antibody breadth and provide durable protection from SARS-CoV-2

The immune responses to Novavax's licensed NVX-CoV2373 nanoparticle Spike protein vaccine against SARS-CoV-2 remain incompletely understood. Here, we show in rhesus macaques that immunization with Matrix-MTM adjuvanted vaccines predominantly elicits immune events in local tissues with little spillover to the periphery. A third dose of an updated vaccine based on the Gamma (P.1) variant 7 months after two immunizations with licensed NVX-CoV2373 resulted in significant enhancement of anti-spike antibody titers and antibody breadth including neutralization of forward drift Omicron variants. The third immunization expanded the Spike-specific memory B cell pool, induced significant somatic hypermutation, and increased serum antibody avidity, indicating considerable affinity maturation. Seven months after immunization, vaccinated animals controlled infection by either WA-1 or P.1 strain, mediated by rapid anamnestic antibody and T cell responses in the lungs. In conclusion, a third immunization with an adjuvanted, low-dose recombinant protein vaccine significantly improved the quality of B cell responses, enhanced antibody breadth, and provided durable protection against SARS-CoV-2 challenge.

Rational prediction of immunogenicity clustering through cross-reactivity analysis of thirteen SARS-CoV-2 variants

SARS-CoV-2 breakthrough infections in vaccinated individuals underscore the threat posed by continuous mutating variants, such as Omicron, to vaccine-induced immunity. This necessitates the search for broad-spectrum immunogens capable of countering infections from such variants. This study evaluates the immunogenicity relationship among SARS-CoV-2 variants, from D614G to XBB, through Guinea pig vaccination, covering D614G, Alpha, Beta, Gamma, Delta, BA.1, BA.2, BA.2.75, BA.2.75.2, BA.5, BF.7, BQ.1.1, and XBB, employing three immunization strategies: three-dose monovalent immunogens, three-dose bivalent immunogens, and a two-dose vaccination with D614G followed by a booster immunization with a variant strain immunogen. Three distinct immunogenicity clusters were identified: D614G, Alpha, Beta, Gamma, and Delta as cluster 1, BA.1, BA.2, and BA.2.75 as cluster 2, BA.2.75.2, BA.5, BF.7, BQ.1.1, and XBB as cluster 3. Broad-spectrum protection could be achieved through a combined immunization strategy using bivalent immunogens or D614G and XBB, or two initial D614G vaccinations followed by two XBB boosters. A comparison of neutralizing antibody levels induced by XBB boosting and equivalent dosing of D614G and XBB revealed that the XBB booster produced higher antibody levels. The study suggests that vaccine antigen selection should focus on the antigenic alterations among variants, eliminating the need for updating vaccine components for each variant.

COVID-19 Vaccination in Pregnancy: Pilot Study for Maternal and Neonatal MicroRNA Profiles

This pilot study explores alterations in miRNA profiles among pregnant women and their neonates upon receiving different doses of COVID-19 vaccines. Blood samples, including maternal blood (MB) and neonatal cord blood (CB), collected from five pregnant women were scrutinized using the miRNA PanelChip Analysis System, identifying nine distinct miRNAs, including miR-451a and miR-1972, which exhibited significant downregulation with two vaccine doses in both MB and CB. When compared with women vaccinated with four doses, miR-486-5p, miR-451a, and miR-1972 in the two-dose group also showed notable downregulation. Evaluating recipients of three and four doses, miR-423-5p and miR-1972 expression were significantly reduced in both MB and CB. Further comparative analysis highlighted a decline in miR-223-3p expression with increasing vaccine doses, while miR15a-5p, miR-16-5p, and miR-423-5p showed an upward trend. Notably, miR-451a, miR-1972, and miR-423-5p levels varied across doses and were associated with pathways such as "PI3K-Akt", "neurotrophin signaling", and "cortisol synthesis", suggesting the profound influence of vaccination on diverse molecular mechanisms. Our research has uncovered that escalating vaccine dosages impact miRNA profiles, which may be associated with the immunological response mechanisms in both the mother and fetus, thus indicating a substantial impact of vaccination on various molecular processes.

Novel Spike-stabilized trimers with improved production protect K18-hACE2 mice and golden Syrian hamsters from the highly pathogenic SARS-CoV-2 Beta variant

Most COVID-19 vaccines are based on the SARS-CoV-2 Spike glycoprotein (S) or their subunits. However, S shows some structural instability that limits its immunogenicity and production, hampering the development of recombinant S-based vaccines. The introduction of the K986P and V987P (S-2P) mutations increases the production and immunogenicity of the recombinant S trimer, suggesting that these two parameters are related. Nevertheless, S-2P still shows some molecular instability and it is produced with low yield. Here we described a novel set of mutations identified by molecular modeling and located in the S2 region of the S-2P that increase its production up to five-fold. Besides their immunogenicity, the efficacy of two representative S-2P-based mutants, S-29 and S-21, protecting from a heterologous SARS-CoV-2 Beta variant challenge was assayed in K18-hACE2 mice (an animal model of severe SARS-CoV-2 disease) and golden Syrian hamsters (GSH) (a moderate disease model). S-21 induced higher level of WH1 and Delta variants neutralizing antibodies than S-2P in K18-hACE2 mice three days after challenge. Viral load in nasal turbinate and oropharyngeal samples were reduced in S-21 and S-29 vaccinated mice. Despite that, only the S-29 protein protected 100% of K18-hACE2 mice from severe disease. When GSH were analyzed, all immunized animals were protected from disease development irrespectively of the immunogen they received. Therefore, the higher yield of S-29, as well as its improved immunogenicity and efficacy protecting from the highly pathogenic SARS-CoV-2 Beta variant, pinpoint the S-29 mutant as an alternative to the S-2P protein for future SARS-CoV-2 vaccine development.

Interim results from a phase I randomized, placebo-controlled trial of novel SARS-CoV-2 beta variant receptor-binding domain recombinant protein and mRNA vaccines as a 4th dose booster

BACKGROUND

SARS-CoV-2 booster vaccination should ideally enhance protection against variants and minimise immune imprinting. This Phase I trial evaluated two vaccines targeting SARS-CoV-2 beta-variant receptor-binding domain (RBD): a recombinant dimeric RBD-human IgG1 Fc-fusion protein, and an mRNA encoding a membrane-anchored RBD.

METHODS

76 healthy adults aged 18-64 y, previously triple vaccinated with licensed SARS-CoV-2 vaccines, were randomised to receive a 4th dose of either an adjuvanted (MF59®, CSL Seqirus) protein vaccine (5, 15 or 45 μg, N = 32), mRNA vaccine (10, 20, or 50 μg, N = 32), or placebo (saline, N = 12) at least 90 days after a 3rd boost vaccination or SARS-CoV-2 infection. Bleeds occurred on days 1 (prior to vaccination), 8, and 29.

CLINICALTRIALS

govNCT05272605.

FINDINGS

No vaccine-related serious or medically-attended adverse events occurred. The protein vaccine reactogenicity was mild, whereas the mRNA vaccine was moderately reactogenic at higher dose levels. Best anti-RBD antibody responses resulted from the higher doses of each vaccine. A similar pattern was seen with live virus neutralisation and surrogate, and pseudovirus neutralisation assays. Breadth of immune response was demonstrated against BA.5 and more recent omicron subvariants (XBB, XBB.1.5 and BQ.1.1). Binding antibody titres for both vaccines were comparable to those of a licensed bivalent mRNA vaccine. Both vaccines enhanced CD4+ and CD8+ T cell activation.

INTERPRETATION

There were no safety concerns and the reactogenicity profile was mild and similar to licensed SARS-CoV-2 vaccines. Both vaccines showed strong immune boosting against beta, ancestral and omicron strains.

FUNDING

Australian Government Medical Research Future Fund, and philanthropies Jack Ma Foundation and IFM investors.

Omicron Variant-Specific Serological Imprinting Following BA.1 or BA.4/5 Bivalent Vaccination and Previous SARS-CoV-2 Infection: A Cohort Study

BACKGROUND

Continuous evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outpaces monovalent vaccine cross-protection to new viral variants. Consequently, bivalent coronavirus disease 2019 (COVID-19) vaccines including Omicron antigens were developed. The contrasting immunogenicity of the bivalent vaccines and the impact of prior antigenic exposure on new immune imprinting remains to be clarified.

METHODS

In the large prospective ENFORCE cohort, we quantified spike-specific antibodies to 5 Omicron variants (BA.1 to BA.5) before and after BA.1 or BA.4/5 bivalent booster vaccination to compare Omicron variant-specific antibody inductions. We evaluated the impact of previous infection and characterized the dominant antibody responses.

RESULTS

Prior to the bivalent fourth vaccine, all participants (N = 1697) had high levels of Omicron-specific antibodies. Antibody levels were significantly higher in individuals with a previous polymerase chain reaction positive (PCR+) infection, particularly for BA.2-specific antibodies (geometric mean ratio [GMR] 6.79, 95% confidence interval [CI] 6.05-7.62). Antibody levels were further significantly boosted in all individuals by receiving either of the bivalent vaccines, but greater fold inductions to all Omicron variants were observed in individuals with no prior infection. The BA.1 bivalent vaccine generated a dominant response toward BA.1 (adjusted GMR 1.31, 95% CI 1.09-1.57) and BA.3 (1.32, 1.09-1.59) antigens in individuals with no prior infection, whereas the BA.4/5 bivalent vaccine generated a dominant response toward BA.2 (0.87, 0.76-0.98), BA.4 (0.85, 0.75-0.97), and BA.5 (0.87, 0.76-0.99) antigens in individuals with a prior infection.

CONCLUSIONS

Vaccination and previous infection leave a clear serological imprint that is focused on the variant-specific antigen. Importantly, both bivalent vaccines induce high levels of Omicron variant-specific antibodies, suggesting broad cross-protection of Omicron variants.

Beta-spike-containing boosters induce robust and functional antibody responses to SARS-CoV-2 in macaques primed with distinct vaccines

The reduced effectiveness of COVID-19 vaccines due to the emergence of variants of concern (VOCs) necessitated the use of vaccine boosters to bolster protection against disease. However, it remains unclear how boosting expands protective breadth when primary vaccine platforms are distinct and how boosters containing VOC spike(s) broaden humoral responses. Here, we report that boosters composed of recombinant spike antigens of ancestral (prototype) and Beta VOCs elicit a robust, pan-VOC, and multi-functional humoral response in non-human primates largely independent of the primary vaccine series platform. Interestingly, Beta-spike-containing boosters stimulate immunoglobulin A (IgA) with a greater breadth of recognition in protein-primed recipients when administered with adjuvant system 03 (AS03). Our results highlight the utility of a component-based booster strategy for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) for broad humoral recognition, independent of primary vaccine series. This is of high global health importance given the heterogeneity of primary vaccination platforms distributed.

Advax-CpG55.2-adjuvanted monovalent or trivalent SARS-CoV-2 recombinant spike protein vaccine protects hamsters against heterologous infection with Beta or Delta variants

The ongoing evolution of SARS-CoV-2 variants emphasizes the need for vaccines providing broad cross-protective immunity. This study was undertaken to assess the ability of Advax-CpG55.2 adjuvanted monovalent recombinant spike protein (Wuhan, Beta, Gamma) vaccines or a trivalent formulation to protect hamsters againstBeta or Delta virus infection. The ability of vaccines to block virus transmission to naïve co-housed animals was also assessed. In naïve hosts, the Beta variant induced higher virus loads than the Delta variant, and conversely the Delta variant caused more severe disease and was more likely to be associated with virus transmission. The trivalent vaccine formulation provided the best protection against both Beta and Delta infection and also completely prevented virus transmission. The next best performing vaccine was the original monovalent Wuhan-based vaccine. Notably, hamsters that received the monovalent Gamma spike vaccine had the highest viral loads and clinical disease of all the vaccine groups, a potential signal of antibody dependent-enhancement (ADE). These hamsters were also the most likely to transmit Delta virus to naïve recipients. In murine studies, the Gamma spike vaccine induced the highest total spike protein to RBD IgG ratio and the lowest levels of neutralizing antibody, a context that could predispose to ADE. Overall, the study results confirmed that the current SpikoGen® vaccine based on Wuhan spike protein was still able to protect against clinical disease caused by either the Beta or Delta virus variants but suggested additional protection may be obtained by combining it with extra variant spike proteins to make a multivalent formulation. This study highlights the complexity of optimizing vaccine protection against multiple SARS-CoV-2 variants and stresses the need to continue to pursue new and improved COVID-19 vaccines able to provide robust, long-lasting, and broadly cross-protective immunity against constantly evolving SARS-CoV-2 variants.

Challenges and Prospects in Developing Future SARS-CoV-2 Vaccines: Overcoming Original Antigenic Sin and Inducing Broadly Neutralizing Antibodies

The impacts of the COVID-19 pandemic led to the development of several effective SARS-CoV-2 vaccines. However, waning vaccine efficacy as well as the antigenic drift of SARS-CoV-2 variants has diminished vaccine efficacy against SARS-CoV-2 infection and may threaten public health. Increasing interest has been given to the development of a next generation of SARS-CoV-2 vaccines with increased breadth and effectiveness against SARS-CoV-2 infection. In this Brief Review, we discuss recent work on the development of these next-generation vaccines and on the nature of the immune response to SARS-CoV-2. We examine recent work to develop pan-coronavirus vaccines as well as to develop mucosal vaccines. We further discuss challenges associated with the development of novel vaccines including the need to overcome "original antigenic sin" and highlight areas requiring further investigation. We place this work in the context of SARS-CoV-2 evolution to inform how the implementation of future vaccine platforms may impact human health.

Comparative Effectiveness of Bivalent (Original/Omicron BA.4/BA.5) COVID-19 Vaccines in Adults

The emergence of Omicron variants coincided with declining vaccine-induced protection against SARS-CoV-2. Two bivalent mRNA vaccines, mRNA-1273.222 (Moderna) and BNT162b2 Bivalent (Pfizer-BioNTech), were developed to provide greater protection against the predominate circulating variants by including mRNA that encodes both the ancestral (original) strain and BA.4/BA.5. We estimated their relative vaccine effectiveness (rVE) in preventing COVID-19-related outcomes in the US using a nationwide dataset linking primary care electronic health records and pharmacy/medical claims data. The study population (aged ≥18 years) received either vaccine between 31 August 2022 and 28 February 2023. We used propensity score weighting to adjust for baseline differences between groups. We estimated the rVE against COVID-19-related hospitalizations (primary outcome) and outpatient visits (secondary) for 1,034,538 mRNA-1273.222 and 1,670,666 BNT162b2 Bivalent vaccine recipients, with an adjusted rVE of 9.8% (95% confidence interval: 2.6-16.4%) and 5.1% (95% CI: 3.2-6.9%), respectively, for mRNA-1273.222 versus BNT162b2 Bivalent. The incremental relative effectiveness was greater among adults ≥ 65; the rVE against COVID-19-related hospitalizations and outpatient visits in these patients was 13.5% (95% CI: 5.5-20.8%) and 10.7% (8.2-13.1%), respectively. Overall, we found greater effectiveness of mRNA-1273.222 compared with the BNT162b2 Bivalent vaccine in preventing COVID-19-related hospitalizations and outpatient visits, with increased benefits in older adults.

Immune imprinting and next-generation coronavirus vaccines

Vaccines based on historical virus isolates provide limited protection from continuously evolving RNA viruses, such as influenza viruses or coronaviruses, which occasionally spill over between animals and humans. Despite repeated booster immunizations, population-wide declines in the neutralization of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants have occurred. This has been compared to seasonal influenza vaccinations in humans, where the breadth of immune responses induced by repeat exposures to antigenically distinct influenza viruses is confounded by pre-existing immunity-a mechanism known as imprinting. Since its emergence, SARS-CoV-2 has evolved in a population with partial immunity, acquired by infection, vaccination or both. Here we critically examine the evidence for and against immune imprinting in host humoral responses to SARS-CoV-2 and its implications for coronavirus disease 2019 (COVID-19) booster vaccine programmes.

Immunogenicity and safety of AZD2816, a beta (B.1.351) variant COVID-19 vaccine, and AZD1222 (ChAdOx1 nCoV-19) as third-dose boosters for previously vaccinated adults: a multicentre, randomised, partly double-blinded, phase 2/3 non-inferiority immunobridging study in the UK and Poland

BACKGROUND

This study aimed to evaluate AZD2816, a variant-updated COVID-19 vaccine expressing the full-length SARS-CoV-2 beta (B.1.351) variant spike protein that is otherwise similar to AZD1222 (ChAdOx1 nCoV-19), and AZD1222 as third-dose boosters.

METHODS

This phase 2/3, partly double-blinded, randomised, active-controlled study was done at 19 sites in the UK and four in Poland. Adult participants who had received a two-dose AZD1222 or mRNA vaccine primary series were randomly assigned by means of an Interactive Response Technology-Randomisation and Trial Supply Management system (1:1 within each primary-series cohort, stratified by age, sex, and comorbidities) to receive AZD1222 or AZD2816 (intramuscular injection; 5 × 1010 viral particles). Participants, investigators, and all sponsor staff members involved in study conduct were masked to randomisation. AZD1222 and AZD2816 doses were prepared by unmasked study staff members. The primary objectives were to evaluate safety and humoral immunogenicity (non-inferiority of day-29 pseudovirus neutralising antibody geometric mean titre [GMT] against ancestral SARS-CoV-2: AZD1222 booster vs AZD1222 primary series [historical controls]; margin 0·67; SARS-CoV-2-seronegative participants). This study is registered with ClinicalTrials.gov, NCT04973449, and is completed.

FINDINGS

Between June 27 and Sept 30, 2021, 1394 participants of the 1741 screened were randomly assigned to AZD1222 or AZD2816 following an AZD1222 (n=373, n=377) or mRNA vaccine (n=322, n=322) primary series. In SARS-CoV-2-seronegative participants receiving AZD1222 or AZD2816, 78% and 80% (AZD1222 primary series) and 90% and 93%, respectively (mRNA vaccine primary series) reported solicited adverse events to the end of day 8; 2%, 2%, 1%, and 1% had serious adverse events and 12%, 12%, 10%, and 11% had adverse events of special interest, respectively, to the end of day 180. The primary immunogenicity non-inferiority endpoint was met: day-29 neutralising antibody GMT ratios (ancestral SARS-CoV-2) were 1·02 (95% CI 0·90-1·14) and 3·47 (3·09-3·89) with AZD1222 booster versus historical controls (AZD1222 and mRNA vaccine primary series, respectively). Responses against beta were greater with AZD2816 versus AZD1222 (GMT ratios, AZD1222, mRNA vaccine primary series 1·84 [1·63-2·08], 2·22 [1·99-2·47]).

INTERPRETATION

Both boosters were well tolerated, with immunogenicity against ancestral SARS-CoV-2 similar to AZD1222 primary-series vaccination. AZD2816 gave greater immune responses against beta versus AZD1222.

FUNDING

AstraZeneca.

The Effectiveness of Bivalent COVID-19 Vaccination: A Preliminary Report

Vaccination has been a game-changer in the long battle against COVID-19. However, waning vaccine-induced immunity and the immune evasion of emerging variants create challenges. The rapid-fire development of bivalent vaccines (BVs), comprising ancestral strains and a new variant, was authorized to prevent COVID-19, but the effectiveness of the updated vaccines remains largely unclear. Electronic databases were searched to investigate the immunogenicity and reactogenicity of BVs in humans. As of March 2023, 20 trials were identified. Compared with monovalent vaccination, the induced immunogenicity against ancestral strains was similar. The BVs demonstrated approximately 33-50% higher immunogenicity values against additional variant strains. An observational cohort study showed the additional clinical effectiveness of the BVs. The adverse events were similar. In conclusion, our systematic review found that the BVs had equal immunogenicity against ancestral strains without safety concerns. Approximately 33-50% increased additional antibody titers and clinical effectiveness against additional variant strains were observed in subjects with a BV vaccine with moderate heterogeneity, especially for BA.1-containing BVs.

Sequential reinfection with Omicron variants elicits broader neutralizing antibody profiles in booster vaccinees and reduces the duration of viral shedding

The constant emergence of breakthrough infections with Omicron variants poses an escalating challenge to the current vaccination strategy. In this study, we investigated the distinct neutralization activities and clinical characteristics of the booster vaccinees with Omicron reinfection compared with single breakthrough infection and homologous booster vaccination. Our results demonstrate that neutralizing antibody GMTs for WT and other four subvariants (BA.2.2, BA.5.2, BF.7, and XBB.1) differ greatly between breakthrough infection and homologous booster cohorts. Sequential reinfection with Omicron variants elicits broader and high-titer variant-specific neutralizing antibody profiles against Omicron variants. It could also dampen the hyperactivation of WT-specific neutralization induced by previous WT-based vaccination. Moreover, the clinical characteristics from reinfection demonstrated that repeated stimulation by Omicron variants could reduce the duration of viral shedding. By considering reinfection with the Omicron variant as a representative model of repeated immunogen exposures, our results thus illustrate the potential superiority of repeated Omicron stimuli and provide additional evidence supporting the Omicron immunogen as a more effective vaccine candidate to mitigate the transmission of emerging variants.

Safety and immunogenicity of multivalent SARS-CoV-2 protein vaccines: a randomized phase 3 trial

Background

COVID-19 vaccines that offer broad-spectrum protection are needed. We aimed to evaluate the safety and immunogenicity of multivalent vaccines, SCTV01E and SCTV01C, and compare them with an inactivated vaccine.

Methods

In the phase 3 trial (ClinicalTrials.gov: NCT05323461), adult participants previously vaccinated with Sinopharm's inactivated SARS-CoV-2 vaccine (BBBIP-CorV) were assigned to receive one booster dose of BBBIP-CorV, 20 μg SCTV01C, or 30 μg SCTV01E. The primary endpoint was to evaluate the geometric mean titers (GMT) of neutralizing antibody (nAb) against the Delta and Omicron BA.1 variants on day 28 after injection. Additional endpoints included GMTs of nAb against Delta (B.1.617.2) and Omicron BA.1 variants on day 180, GMTs against BA.5 on day 28, as well as solicited adverse events (AEs) within seven days, unsolicited AEs within 28 days, and serious AEs, AEs of special interest within 180 days after vaccination.

Findings

Between May 30, 2022 and October 28, 2022, a total of 1351 participants were randomized to BBBIP-CorV, SCTV01C, or SCTV01E in a 1:1:1 ratio, with immunogenicity assessments performed on the first 300 participants. For BBBIP-CorV, SCTV01C, and SCTV01E groups, the day 28 GMTs of neutralizing antibody against Omicron BA.1 were a 2.38-, 19.37-, and 28.06-fold increase from baseline; the GMTs against Omicron BA.5 were 2.07-, 15.89- and 21.11-fold increases; the GMTs against Delta variants were 1.97-, 12.76-, and 15.88-fold increases, respectively. The day 28 geometric mean ratio (GMR) of SCTV01C/BBIBP-CorV for Omicron BA.1 was 6.49 (95% CI: 4.75, 8.88), while the GMR of SCTV01E/BBIBP-CorV was 9.56 (95% CI: 6.85, 13.33). For the Delta variant, the day 28 GMR of SCTV01C/BBIBP-CorV was 6.26 (95% CI: 4.78, 8.19), and the day 28 GMR of SCTV01E/BBIBP-CorV was 7.26 (95% CI: 5.51, 9.56). On Day 180, the GMTs against Omicron BA.1 were 2.80-, 9.51-, and 15.56-fold increase from baseline, while those against Delta were 1.58-, 5.49-, and 6.63-fold for BBBIP-CorV, SCTV01C, and SCTV01E groups, respectively. Subgroup analyses showed that SCTV01C and SCTV01E induced uniformly high GMTs against both BA.1 and BA.5, demonstrating its superiority over BBIBP-CorV, regardless of baseline GMT levels. Safety and reactogenicity were similar among the three vaccines. Most AEs were Grade 1 or 2. There were 15 ≥Grade 3 AEs: 6 in the BBIBP-CorV group, 4 in the SCTV01C group and 5 in the SCTV01E group. No SAE was reported and one grade 1 AESI (Bell's palsy) was observed in SCTV01C group.

Interpretation

A booster dose of the tetravalent vaccine SCTV01E consistently induced high neutralizing antibody responses against Omicron BA.1, BA.5, and Delta variants, demonstrating superiority over inactivated vaccine. There is evidence to suggest that SCTV01E may have GMT superiority over bivalent vaccine SCTV01C against Delta, BA.1 and BA.5 variants.

Funding

This study was sponsored by Sinocelltech Ltd., and funded by the Beijing Science and Technology Planning Project [Z221100007922012] and the National Key Research and Development Program of China [2022YFC0870600].

mRNA vaccines against respiratory viruses

PURPOSE OF REVIEW

The successes of the coronavirus disease 2019 (COVID-19) mRNA vaccines have accelerated the development of mRNA vaccines against other respiratory pathogens. The aim of this review is to highlight COVID-19 mRNA vaccine advances and provide an update on the progress of mRNA vaccine development against other respiratory pathogens.

RECENT FINDINGS

The COVID-19 mRNA vaccines demonstrated effectiveness in preventing severe COVID-19 and death. H7N9 and H10N8 avian influenza mRNA vaccines have demonstrated safety and immunogenicity in phase 1 clinical trials. Numerous seasonal influenza mRNA vaccines are in phase 1-3 clinical trials. Respiratory syncytial virus (RSV) mRNA vaccines have progressed to phase 2-3 clinical trials in adults and a phase 1 clinical trial in children. A combined human metapneumovirus and parainfluenza-3 mRNA vaccines was found to be well tolerated and immunogenic in a phase 1 trial among adults and trials are being conducted among children. Clinical trials of mRNA vaccines combining antigens from multiple respiratory viruses are underway.

SUMMARY

The development of mRNA vaccines against respiratory viruses has progressed rapidly in recent years. Promising vaccine candidates are moving through the clinical development pathway to test their efficacy in preventing disease against respiratory viral pathogens.

Comparison of bivalent and monovalent SARS-CoV-2 variant vaccines: the phase 2 randomized open-label COVAIL trial

Vaccine protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection wanes over time, requiring updated boosters. In a phase 2, open-label, randomized clinical trial with sequentially enrolled stages at 22 US sites, we assessed safety and immunogenicity of a second boost with monovalent or bivalent variant vaccines from mRNA and protein-based platforms targeting wild-type, Beta, Delta and Omicron BA.1 spike antigens. The primary outcome was pseudovirus neutralization titers at 50% inhibitory dilution (ID50 titers) with 95% confidence intervals against different SARS-CoV-2 strains. The secondary outcome assessed safety by solicited local and systemic adverse events (AEs), unsolicited AEs, serious AEs and AEs of special interest. Boosting with prototype/wild-type vaccines produced numerically lower ID50 titers than any variant-containing vaccine against all variants. Conversely, boosting with a variant vaccine excluding prototype was not associated with decreased neutralization against D614G. Omicron BA.1 or Beta monovalent vaccines were nearly equivalent to Omicron BA.1 + prototype or Beta + prototype bivalent vaccines for neutralization of Beta, Omicron BA.1 and Omicron BA.4/5, although they were lower for contemporaneous Omicron subvariants. Safety was similar across arms and stages and comparable to previous reports. Our study shows that updated vaccines targeting Beta or Omicron BA.1 provide broadly crossprotective neutralizing antibody responses against diverse SARS-CoV-2 variants without sacrificing immunity to the ancestral strain. ClinicalTrials.gov registration: NCT05289037 .

COVID-19 Bivalent Booster in Pregnancy: Maternal and Neonatal Antibody Response to Omicron BA.5, BQ.1, BF.7 and XBB.1.5 SARS-CoV-2

Our study was to investigate the effects of bivalent COVID-19 booster vaccination during pregnancy on neutralizing antibody (Nab) levels in maternal blood (MB), transplacental transmission in umbilical cord blood (CB), and efficacy against Omicron SARS-CoV-2 subvariants including BA.5, BF.7, BQ.1, and XBB.1.5. We collected MB and CB from 11 pregnant participants during baby delivery and detected Nab inhibition by enzyme-linked immunosorbent assays (ELISA). Nab inhibition was 89-94% in MB and 82-89% in CB for Omicron subvariants. Those receiving AZD1222 vaccines in previous monovalent vaccination demonstrated poorer maternal Nab inhibition of BA.5, BQ.1, and XBB.1.5 than others. Poorer maternal Nab inhibition of BA.5, BF.7, and BQ.1 was found in those receiving two-dose AZD1222 vaccinations than with either one or no AZD1222 vaccination. MB from those with infants weighing < 3100 g demonstrated better Nab inhibition of BF.7 than those > 3100 g (97.99 vs. 95.20%, p = 0.048), and there were also similar trends for Nab inhibition of BA.5 and BQ.1. No significant differences were seen in CB samples. Although diminished maternal Nab inhibition was seen in those with previous monovalent AZD1222 vaccination and heavier newborns, neonatal Nab inhibition was still strong after bivalent COVID-19 booster vaccination.

Three-month antibody persistence of a bivalent Omicron-containing booster vaccine against COVID-19

We previously presented day 29 interim safety and immunogenicity results from a phase 2/3 study (NCT04927065) comparing the Omicron-BA.1-containing bivalent vaccine mRNA-1273.214 (50-µg) to the 50-µg mRNA-1273 booster in adults who previously received the mRNA-1273 primary series (100-µg) and mRNA-1273 first booster (50-µg) dose. Primary endpoints were safety, non-inferiority of the neutralizing antibody (nAb) and seroresponse against Omicron BA.1, superiority of the nAb response against Omicron-BA.1, and non-inferiority of the nAb response against ancestral SARS-CoV-2 for second boosters of mRNA-1273.214 versus mRNA-1273 at days 29 and 91. The key secondary endpoint was the seroresponse difference of mRNA-1273.214 versus mRNA-1273 against ancestral SARS-CoV-2 at days 29 and day 91. Participants were sequentially enrolled and dosed with 50-µg of mRNA-1273 (n = 376) or mRNA-1273.214 (n = 437) as second booster doses. Here we present day 91 post-booster results. In participants with no pre-booster, severe acute respiratory syndrome coronavirus 2-infection (SARS-CoV-2), mRNA-1273.214 elicited Omicron-BA.1-nAb titers (95% confidence interval [CI]) that were significantly higher (964.4 [834.4-1114.7]) than those of mRNA-1273 (624.2 [533.1-730.9]) and similar to those of mRNA-1273 against ancestral SARS-CoV-2 at day 91. mRNA-1273.214 also induced higher binding antibody responses against Omicron BA.1 and alpha, gamma and delta variants than mRNA-1273. Safety profiles were similar for both vaccines. The Omicron-BA.1 bivalent vaccine improved antibody responses compared to mRNA-1273 through 90 days post-booster.

Hybrid Immunity Provides the Best COVID-19 Humoral Response in Immunocompromised Patients with or without SARS-CoV-2 Infection History

Immunization against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has significantly limited the spread of coronavirus disease 2019 (COVID-19) and reduced the associated complications, especially mortality. To prolong immunity, an immune booster was implemented. We evaluated the role of SARS-CoV-2 infection history in the vaccination schedules of kidney and liver transplant recipients and patients with chronic kidney disease (CKD). To this end, we retrospectively analyzed the data of 78 solid organ transplantation (SOT) recipients and 40 patients with immunoglobulin A (IgA) nephropathy as representatives of the CKD group. Patients received two or three doses of the BNT162b2 vaccine. At the follow-up, antibody (Ab) titer, graft function, COVID-19 history, and patients' clinical condition were assessed. Ab level was higher after two doses in patients with a COVID-19 history over three doses in patients with no COVID-19 history. Compared to three doses, subjects who were administered two doses had a longer median time to infection. Positive antibodies, in response to the third dose, were not observed in up to 8.4% of SOT patients. The results show that the vaccination schedule should take into account the vaccine response rate and COVID-19 history. So-called hybrid immunity appears to be most efficient at providing humoral responses against SARS-CoV-2 infection in immunocompromised patients.

Changes in Population Immunity Against Infection and Severe Disease From Severe Acute Respiratory Syndrome Coronavirus 2 Omicron Variants in the United States Between December 2021 and November 2022

BACKGROUND

Although a substantial fraction of the US population was infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during December 2021-February 2022, the subsequent evolution of population immunity reflects the competing influences of waning protection over time and acquisition or restoration of immunity through additional infections and vaccinations.

METHODS

Using a Bayesian evidence synthesis model of reported coronavirus disease 2019 (COVID-19) data (diagnoses, hospitalizations), vaccinations, and waning patterns for vaccine- and infection-acquired immunity, we estimate population immunity against infection and severe disease from SARS-CoV-2 Omicron variants in the United States, by location (national, state, county) and week.

RESULTS

By 9 November 2022, 97% (95%-99%) of the US population were estimated to have prior immunological exposure to SARS-CoV-2. Between 1 December 2021 and 9 November 2022, protection against a new Omicron infection rose from 22% (21%-23%) to 63% (51%-75%) nationally, and protection against an Omicron infection leading to severe disease increased from 61% (59%-64%) to 89% (83%-92%). Increasing first booster uptake to 55% in all states (current US coverage: 34%) and second booster uptake to 22% (current US coverage: 11%) would increase protection against infection by 4.5 percentage points (2.4-7.2) and protection against severe disease by 1.1 percentage points (1.0-1.5).

CONCLUSIONS

Effective protection against SARS-CoV-2 infection and severe disease in November 2022 was substantially higher than in December 2021. Despite this high level of protection, a more transmissible or immune evading (sub)variant, changes in behavior, or ongoing waning of immunity could lead to a new SARS-CoV-2 wave.

Safety and immunogenicity of a SARS-CoV-2 Gamma variant RBD-based protein adjuvanted vaccine used as booster in healthy adults

A Gamma Variant RBD-based aluminum hydroxide adjuvanted vaccine called ARVAC CG was selected for a first in human clinical trial. Healthy male and female participants (18-55 years old) with a complete COVID-19-primary vaccine scheme were assigned to receive two intramuscular doses of either a low-dose or a high-dose of ARVAC CG. The primary endpoint was safety. The secondary objective was humoral immunogenicity. Cellular immune responses were studied as an exploratory objective. The trial was prospectively registered in PRIISA.BA (Registration Code 6564) and ANMAT and retrospectively registered in ClinicalTrials.gov (NCT05656508). Samples from participants of a surveillance strategy implemented by the Ministry of Health of the Province of Buenos Aires that were boosted with BNT162b2 were also analyzed to compare with the booster effect of ARVAC CG. ARVAC CG exhibits a satisfactory safety profile, a robust and broad booster response of neutralizing antibodies against the Ancestral strain of SARS-CoV-2 and the Gamma, Delta, Omicron BA.1 and Omicron BA.5 variants of concern and a booster effect on T cell immunity in individuals previously immunized with different COVID-19 vaccine platforms.

Safety and immunogenicity of a tetravalent and bivalent SARS-CoV-2 protein booster vaccine in men

The safety and immunogenicity of a protein-based tetravalent vaccine SCTV01E that contains spike protein ectodomain (S-ECD) of Alpha, Beta, Delta and Omicron BA.1 are assessed and compared with bivalent protein vaccine SCTV01C (Alpha and Beta variants) and monovalent mRNA vaccine (NCT05323461). The primary endpoints are the geometric mean titers (GMT) of live virus neutralizing antibodies (nAb) to Delta (B.1.617.2) and Omicron BA.1 at day 28 post-injection. The secondary endpoints include the safety, day 180 GMTs against Delta and Omicron BA.1, day 28 GMTs to BA.5, and seroresponse rates of neutralizing antibodies and T cell responses at day 28 post-injection. 450 participants, comprising of 449 males and 1 female, with a median age (range) of 27 (18-62) years, are assigned to receive one booster dose of BNT162b2, 20 µg SCTV01C or 30 µg SCTV01E and completed 4-week follow-up. All SCTV01E related adverse events (AEs) are mild or moderate and no Grade ≥3 AE, serious AE or new safety concerns are identified. Day 28 GMT of live virus neutralizing antibodies and seroresponse against Omicron BA.1 and BA.5 with SCTV01E are significantly higher than those with SCTV01C and BNT162b2. These data indicate an overall neutralization superiority with tetravalent booster immunization in men.

Neutralizing antibody levels associated with injectable and aerosolized Ad5-nCoV boosters and BA.2 infection

BACKGROUND

Several COVID-19 vaccines are in widespread use in China. Few data exist on comparative immunogenicity of different COVID-19 vaccines given as booster doses. We aimed to assess neutralizing antibody levels raised by injectable and inhaled aerosolized recombinant adenovirus type 5 (Ad5)-vectored COVID-19 vaccine as a heterologous booster after an inactivated COVID-19 vaccine two-dose primary series.

METHODS

Using an open-label prospective cohort design, we recruited 136 individuals who had received inactivated vaccine primary series followed by either injectable or inhaled Ad5-vectored vaccine and measured neutralizing antibody titers against ancestral SARS-CoV-2 virus and Omicron BA.1 and BA.5 variants. We also measured neutralizing antibody levels in convalescent sera from 39 patients who recovered from Omicron BA.2 infection.

RESULTS

Six months after primary series vaccination, neutralizing immunity against ancestral SARS-CoV-2 was low and neutralizing immunity against Omicron (B.1.1.529) was lower. Boosting with Ad5-vectored vaccines induced a high immune response against ancestral SARS-CoV-2. Neutralizing responses against Omicron BA.5 were ≥ 80% lower than against ancestral SARS-CoV-2 in sera from prime-boost subjects and in convalescent sera from survivors of Omicron BA.2 infection. Inhaled aerosolized Ad5-vectored vaccine was associated with greater neutralizing titers than injectable Ad5-vectored vaccine against ancestral and Omicron SARS-CoV-2 variants.

CONCLUSIONS

These findings support the current strategy of heterologous boosting with injectable or inhaled Ad5-vectored SARS-CoV-2 vaccination of individuals primed with inactivated COVID-19 vaccine.

Bivalent mRNA vaccine effectiveness against SARS-CoV-2 variants of concern

BACKGROUND

Sequential infections with SARS-CoV-2 variants such as Alpha, Delta, Omicron and its sublineages may cause high morbidity, so it is necessary to develop vaccines that can protect against both wild-type (WT) virus and its variants. Mutations in SARS-CoV-2's spike protein can easily alter viral transmission and vaccination effectiveness.

METHODS

In this study, we designed full-length spike mRNAs for WT, Alpha, Delta, and BA.5 variants and integrated each into monovalent or bivalent mRNA-lipid nanoparticle vaccines. A pseudovirus neutralization assay was conducted on immunized mouse sera in order to examine the neutralizing potential of each vaccine.

RESULTS

Monovalent mRNA vaccines were only effective against the same type of virus. Interestingly, monovalent BA.5 vaccination could neutralize BF.7 and BQ.1.1. Moreover, WT, Alpha, Delta, BA.5, and BF.7 pseudoviruses were broadly neutralized by bivalent mRNA vaccinations, such as BA.5 + WT, BA.5 + Alpha, and BA.5 + Delta. In particular, BA.5 + WT exhibited high neutralization against most variants of concern (VOCs) in a pseudovirus neutralization assay.

CONCLUSIONS

Our results show that combining two mRNA sequences may be an effective way to develop a broadly protective SARS-CoV-2 vaccine against a wide range of variant types. Importantly, we provide the optimal combination regimen and propose a strategy that may prove useful in combating future VOCs.

T-cell immunity to SARS-CoV-2: what if the known best is not the optimal course for the long run? Adapting to evolving targets

Humanity did surprisingly well so far, considering how unprepared it was to respond to the coronavirus disease 2019 (COVID-19) threat. By blending old and ingenious new technology in the context of the accumulated knowledge on other human coronaviruses, several vaccine candidates were produced and tested in clinical trials in record time. Today, five vaccines account for the bulk of the more than 13 billion doses administered worldwide. The ability to elicit biding and neutralizing antibodies most often against the spike protein is a major component of the protection conferred by immunization but alone it is not enough to limit virus transmission. Thus, the surge in numbers of infected individuals by newer variants of concern (VOCs) was not accompanied by a proportional increase in severe disease and death rate. This is likely due to antiviral T-cell responses, whose evasion is more difficult to achieve. The present review helps navigating the very large literature on T cell immunity induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and vaccination. We examine the successes and shortcomings of the vaccinal protection in the light of the emergence of VOCs with breakthrough potential. SARS-CoV-2 and human beings will likely coexist for a long while: it will be necessary to update existing vaccines to improve T-cell responses and attain better protection against COVID-19.

The Quantification of Spike Proteins in the Inactivated SARS-CoV-2 Vaccines of the Prototype, Delta, and Omicron Variants by LC-MS

Developing variant vaccines or multivalent vaccines is a feasible way to address the epidemic as the SARS-CoV-2 variants of concern (VOCs) posed an increased risk to global public health. The spike protein of the SARS-CoV-2 virus was usually used as the main antigen in many types of vaccines to produce neutralizing antibodies against the virus. However, the spike (S) proteins of different variants were only differentiated by a few amino acids, making it difficult to obtain specific antibodies that can distinguish different VOCs, thereby challenging the accurate distinction and quantification of the variants using immunological methods such as ELISA. Here, we established a method based on LC-MS to quantify the S proteins in inactivated monovalent vaccines or trivalent vaccines (prototype, Delta, and Omicron strains). By analyzing the S protein sequences of the prototype, Delta, and Omicron strains, we identified peptides that were different and specific among the three strains and synthesized them as references. The synthetic peptides were isotopically labeled as internal targets. Quantitative analysis was performed by calculating the ratio between the reference and internal target. The verification results have shown that the method we established had good specificity, accuracy, and precision. This method can not only accurately quantify the inactivated monovalent vaccine but also could be applied to each strain in inactivated trivalent SARS-CoV-2 vaccines. Hence, the LC-MS method established in this study can be applied to the quality control of monovalent and multivalent SARS-CoV-2 variation vaccines. By enabling more accurate quantification, it will help to improve the protection of the vaccine to some extent.

Bivalent and Monovalent SARS-CoV-2 Variant Vaccine Boosters Improve coverage of the known Antigenic Landscape: Results of the COVID-19 Variant Immunologic Landscape (COVAIL) Trial

Vaccine protection against COVID-19 wanes over time and has been impacted by the emergence of new variants with increasing escape of neutralization. The COVID-19 Variant Immunologic Landscape (COVAIL) randomized clinical trial (clinicaltrials.gov NCT05289037) compares the breadth, magnitude and durability of antibody responses induced by a second COVID-19 vaccine boost with mRNA (Moderna mRNA-1273 and Pfizer-BioNTech BNT162b2), or adjuvanted recombinant protein (Sanofi CoV2 preS DTM-AS03) monovalent or bivalent vaccine candidates targeting ancestral and variant SARS-CoV-2 spike antigens (Beta, Delta and Omicron BA.1). We found that boosting with a variant strain is not associated with loss in neutralization against the ancestral strain. However, while variant vaccines compared to the prototype/wildtype vaccines demonstrated higher neutralizing activity against Omicron BA.1 and BA.4/5 subvariants for up to 3 months after vaccination, neutralizing activity was lower for more recent Omicron subvariants. Our study, incorporating both antigenic distances and serologic landscapes, can provide a framework for objectively guiding decisions for future vaccine updates.

Broad immunity to SARS-CoV-2 variants of concern mediated by a SARS-CoV-2 receptor-binding domain protein vaccine

BACKGROUND

The SARS-CoV-2 global pandemic has fuelled the generation of vaccines at an unprecedented pace and scale. However, many challenges remain, including: the emergence of vaccine-resistant mutant viruses, vaccine stability during storage and transport, waning vaccine-induced immunity, and concerns about infrequent adverse events associated with existing vaccines.

METHODS

We report on a protein subunit vaccine comprising the receptor-binding domain (RBD) of the ancestral SARS-CoV-2 spike protein, dimerised with an immunoglobulin IgG1 Fc domain. These were tested in conjunction with three different adjuvants: a TLR2 agonist R4-Pam2Cys, an NKT cell agonist glycolipid α-Galactosylceramide, or MF59® squalene oil-in-water adjuvant, using mice, rats and hamsters. We also developed an RBD-human IgG1 Fc vaccine with an RBD sequence of the immuno-evasive beta variant (N501Y, E484K, K417N). These vaccines were also tested as a heterologous third dose booster in mice, following priming with whole spike vaccine.

FINDINGS

Each formulation of the RBD-Fc vaccines drove strong neutralising antibody (nAb) responses and provided durable and highly protective immunity against lower and upper airway infection in mouse models of COVID-19. The 'beta variant' RBD vaccine, combined with MF59® adjuvant, induced strong protection in mice against the beta strain as well as the ancestral strain. Furthermore, when used as a heterologous third dose booster, the RBD-Fc vaccines combined with MF59® increased titres of nAb against other variants including alpha, delta, delta+, gamma, lambda, mu, and omicron BA.1, BA.2 and BA.5.

INTERPRETATION

These results demonstrated that an RBD-Fc protein subunit/MF59® adjuvanted vaccine can induce high levels of broadly reactive nAbs, including when used as a booster following prior immunisation of mice with whole ancestral-strain spike vaccines. This vaccine platform offers a potential approach to augment some of the currently approved vaccines in the face of emerging variants of concern, and it has now entered a phase I clinical trial.

FUNDING

This work was supported by grants from the Medical Research Future Fund (MRFF) (2005846), The Jack Ma Foundation, National Health and Medical Research Council of Australia (NHMRC; 1113293) and Singapore National Medical Research Council (MOH-COVID19RF-003). Individual researchers were supported by an NHMRC Senior Principal Research Fellowship (1117766), NHMRC Investigator Awards (2008913 and 1173871), Australian Research Council Discovery Early Career Research Award (ARC DECRA; DE210100705) and philanthropic awards from IFM investors and the A2 Milk Company.

SARS-CoV-2 Omicron boosting induces de novo B cell response in humans

The primary two-dose SARS-CoV-2 mRNA vaccine series are strongly immunogenic in humans, but the emergence of highly infectious variants necessitated additional doses and the development of vaccines aimed at the new variants1-4. SARS-CoV-2 booster immunizations in humans primarily recruit pre-existing memory B cells5-9. However, it remains unclear whether the additional doses induce germinal centre reactions whereby re-engaged B cells can further mature, and whether variant-derived vaccines can elicit responses to variant-specific epitopes. Here we show that boosting with an mRNA vaccine against the original monovalent SARS-CoV-2 mRNA vaccine or the bivalent B.1.351 and B.1.617.2 (Beta/Delta) mRNA vaccine induced robust spike-specific germinal centre B cell responses in humans. The germinal centre response persisted for at least eight weeks, leading to significantly more mutated antigen-specific bone marrow plasma cell and memory B cell compartments. Spike-binding monoclonal antibodies derived from memory B cells isolated from individuals boosted with either the original SARS-CoV-2 spike protein, bivalent Beta/Delta vaccine or a monovalent Omicron BA.1-based vaccine predominantly recognized the original SARS-CoV-2 spike protein. Nonetheless, using a more targeted sorting approach, we isolated monoclonal antibodies that recognized the BA.1 spike protein but not the original SARS-CoV-2 spike protein from individuals who received the mRNA-1273.529 booster; these antibodies were less mutated and recognized novel epitopes within the spike protein, suggesting that they originated from naive B cells. Thus, SARS-CoV-2 booster immunizations in humans induce robust germinal centre B cell responses and can generate de novo B cell responses targeting variant-specific epitopes.

Hybrid Immunity Provides Protective Advantage Over Vaccination or Prior Remote Coronavirus Disease 2019 Alone

Background

The protective efficacy of prior coronavirus disease 2019 (COVID-19) with or without vaccination remains unknown. This study sought to understand if 2 or more messenger RNA (mRNA) vaccine doses provide additional protection in patients with prior infection, or if infection alone provides comparable protection.

Methods

We conducted a retrospective cohort study of the risk of COVID-19 from 16 December 2020 through 15 March 2022, among vaccinated and unvaccinated patients of all ages with and without prior infection. A Simon-Makuch hazard plot illustrated the incidence of COVID-19 between groups. Multivariable Cox proportional hazards regression was used to examine the association of demographics, prior infection, and vaccination status with new infection.

Results

Among 101 941 individuals with at least 1 COVID-19 polymerase chain reaction test prior to 15 March 2022, 72 361 (71.0%) received mRNA vaccination and 5957 (5.8%) were previously infected. The cumulative incidence of COVID-19 was substantially higher throughout the study period for those previously uninfected and unvaccinated, and lowest for those previously infected and vaccinated. After accounting for age, sex, and the interaction between vaccination and prior infection, a reduction in reinfection risk was noted during the Omicron and pre-Omicron phases of 26% (95% confidence interval [CI], 8%-41%; P = .0065) to 36% (95% CI, 10%-54%; P = .0108), respectively, among previously infected and vaccinated individuals, compared to previously infected subjects without vaccination.

Conclusions

Vaccination was associated with lower risk of COVID-19, including in those with prior infection. Vaccination should be encouraged for all including those with prior infection, especially as new variants emerge and variant-specific booster vaccines become available.

Vaccine Confidence and Uptake of the Omicron Bivalent Booster in Tennessee: Implications for Vulnerable Populations

The COVID-19 Omicron variant and its subvariants are now the dominant variants circulating in the US. Therefore, the original COVID-19 vaccine cannot offer full protection. Instead, vaccines that target the spike proteins of the Omicron variants are warranted. Hence, the FDA recommended the development of a bivalent booster. Unfortunately, despite the safety and immunogenicity of the Omicron bivalent boosters from Pfizer and Moderna, uptake in the US has been poor. At this time, only 15.8% of individuals in the US aged five and older have received the Omicron bivalent booster (OBB). The rate is 18% for those aged 18 and older. Poor vaccine confidence and booster uptake are often fueled by misinformation and vaccine fatigue. These result in more problems associated with vaccine hesitancy, which are particular prevalent in Southern states in the US. In Tennessee, the OBB vaccination rate for eligible recipients is only 5.88% at time of writing (16 February 2023). In this review, we discuss (1) the rationale for developing the OBBs; (2) the efficacy and safety of the bivalent boosters; (3) the adverse events associated with these boosters; (4) vaccine hesitancy associated with the OBBs uptake in Tennessee; (5) implications for vulnerable populations, disparities in uptake of OBBs in Tennessee, and strategies to improve vaccine confidence and OBB uptake. In support of public health, it is essential that we continue to provide education, awareness, and vaccine access to the vulnerable and medically underserved populations in Tennessee. Receiving the OBBs is the most effective method to date of protecting the public against severe COVID disease, hospitalization, and death.

Immunogenicity of bivalent omicron (BA.1) booster vaccination after different priming regimens in health-care workers in the Netherlands (SWITCH ON): results from the direct boost group of an open-label, multicentre, randomised controlled trial

BACKGROUND

Bivalent mRNA-based COVID-19 vaccines encoding the ancestral and omicron spike (S) protein were developed as a countermeasure against antigenically distinct SARS-CoV-2 variants. We aimed to assess the (variant-specific) immunogenicity and reactogenicity of mRNA-based bivalent omicron (BA.1) vaccines in individuals who were primed with adenovirus-based or mRNA-based vaccines encoding the ancestral spike protein.

METHODS

We analysed results of the direct boost group of the SWITCH ON study, an open-label, multicentre, randomised controlled trial. Health-care workers from four academic hospitals in the Netherlands aged 18-65 years who had completed a primary COVID-19 vaccination regimen and received one booster of an mRNA-based vaccine, given no later than 3 months previously, were eligible. Participants were randomly assigned (1:1) using computer software in block sizes of 16 and 24 to receive an omicron BA.1 bivalent booster straight away (direct boost group) or a bivalent omicron BA.5 booster, postponed for 90 days (postponed boost group), stratified by priming regimen. The BNT162b2 OMI BA.1 boost was given to participants younger than 45 years, and the mRNA-1273.214 boost was given to participants 45 years or older, as per Dutch guidelines. The direct boost group, whose results are presented here, were divided into four subgroups for analysis: (1) Ad26.COV2.S (Johnson & Johnson) prime and BNT162b2 OMI BA.1 (BioNTech-Pfizer) boost (Ad/P), (2) mRNA-based prime and BNT162b2 OMI BA.1 boost (mRNA/P), (3) Ad26.COV2.S prime and mRNA-1273.214 (Moderna) boost (Ad/M), and (4) mRNA-based prime and mRNA-1273.214 boost (mRNA/M). The primary outcome was fold change in S protein S1 subunit-specific IgG antibodies before and 28 days after booster vaccination. The primary outcome and safety were assessed in all participants except those who withdrew, had a SARS-CoV-2 breakthrough infection, or had a missing blood sample at day 0 or day 28. This trial is registered with ClinicalTrials.gov, NCT05471440.

FINDINGS

Between Sept 2 and Oct 4, 2022, 219 (50%) of 434 eligible participants were randomly assigned to the direct boost group; 187 participants were included in the primary analyses; exclusions were mainly due to SARS-CoV-2 infection between days 0 and 28. From the 187 included participants, 138 (74%) were female and 49 (26%) were male. 42 (22%) of 187 participants received Ad/P and 44 (24%) mRNA/P (those aged <45 years), and 45 (24%) had received Ad/M and 56 (30%) mRNA/M (those aged ≥45 years). S1-specific binding antibody concentrations increased 7 days after bivalent booster vaccination and remained stable over 28 days in all four subgroups (geometric mean ratio [GMR] between day 0 and day 28 was 1·15 [95% CI 1·12-1·19] for the Ad/P group, 1·17 [1·14-1·20] for the mRNA/P group, 1·20 [1·17-1·23] for the Ad/M group, and 1·16 [1·13-1·19] for the mRNA/M group). We observed no significant difference in the GMR between the Ad/P and mRNA/P groups (p=0·51). The GMR appeared to be higher in the Ad/M group than in the mRNA/M group, but was not significant (p=0·073). Most side-effects were mild to moderate in severity and resolved within 48 h in most individuals.

INTERPRETATION

Booster vaccination with mRNA-1273.214 or BNT162b2 OMI BA.1 in adult healthcare workers resulted in a rapid recall of humoral and cellular immune responses independent of the priming regimen. Monitoring of SARS-CoV-2 immunity at the population level, and simultaneously antigenic drift at the virus level, remains crucial to assess the necessity and timing of COVID-19 variant-specific booster vaccinations.

FUNDING

The Netherlands Organization for Health Research and Development (ZonMw).

Immune evasion of neutralizing antibodies by SARS-CoV-2 Omicron

Since its emergence at the end of 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused the infection of more than 600 million people worldwide and has significant damage to global medical, economic, and political structures. Currently, a highly mutated variant of concern, SARS-CoV-2 Omicron, has evolved into many different subvariants mainly including BA.1, BA.2, BA.3, BA.4/5, and the recently emerging BA.2.75.2, BA.2.76, BA.4.6, BA.4.7, BA.5.9, BF.7, BQ.1, BQ.1.1, XBB, XBB.1, etc. Mutations in the N-terminal domain (NTD) of the spike protein, such as A67V, G142D, and N212I, alter the antigenic structure of Omicron, while mutations in the spike receptor binding domain (RBD), such as R346K, Q493R, and N501Y, increase the affinity for angiotensin-converting enzyme 2 (ACE2). Both types of mutations greatly increase the capacity of Omicron to evade immunity from neutralizing antibodies, produced by natural infection and/or vaccination. In this review, we systematically assess the immune evasion capacity of SARS-CoV-2, with an emphasis on the neutralizing antibodies generated by different vaccination regimes. Understanding the host antibody response and the evasion strategies employed by SARS-CoV-2 variants will improve our capacity to combat newly emerging Omicron variants.

Report of consensus panel 5 from the 11th international workshop on Waldenstrom's macroglobulinemia on COVID-19 prophylaxis and management

Consensus Panel 5 (CP5) of the 11th International Workshop on Waldenstrom's Macroglobulinemia (IWWM-11; held in October 2022) was tasked with reviewing the current data on the coronavirus disease-2019 (COVID-19) prophylaxis and management in patients with Waldenstrom's Macroglobulinemia (WM). The key recommendations from IWWM-11 CP5 included the following: Booster vaccines for SARS-CoV-2 should be recommended to all patients with WM. Variant-specific booster vaccines, such as the bivalent vaccine for the ancestral Wuhan strain and the Omicron BA.4.5 strain, are important as novel mutants emerge and become dominant in the community. A temporary interruption in Bruton's Tyrosine Kinase-inhibitor (BTKi) or chemoimmunotherapy before vaccination might be considered. Patients under treatment with rituximab or BTK-inhibitors have lower antibody responses against SARS-CoV-2; thus, they should continue to follow preventive measures, including mask wearing and avoiding crowded places. Patients with WM are candidates for preexposure prophylaxis, if available and relevant to the dominant SARS-CoV-2 strains in a specific area. Oral antivirals should be offered to all symptomatic WM patients with mild to moderate COVID-19 regardless of vaccination, disease status or treatment, as soon as possible after the positive test and within 5 days of COVID-19-related symptom onset. Coadministration of ibrutinib or venetoclax with ritonavir should be avoided. In these patients, remdesivir offers an effective alternative. Patients with asymptomatic or oligosymptomatic COVID-19 should not interrupt treatment with a BTK inhibitor. Infection prophylaxis is essential in patients with WM and include general preventive measures, prophylaxis with antivirals and vaccination against common pathogens including SARS-CoV-2, influenza, and S. pneumoniae.