Safety and immunogenicity of heterologous and homologous inactivated and adenoviral-vectored COVID-19 vaccine regimens in healthy adults: a prospective cohort study

COVID-19 vaccine breakthrough infection among health care workers at MODHS hospitals in Saudi Arabia: A multicenter study

BACKGROUND

We investigated the clinical manifestation and severity of COVID-19 infection represented as a composite outcome (hospital or ICU admission, or in-hospital death) among infected fully vaccinated HCWs, the RT-PCR test Ct value (Cycle Threshold) of positive fully vaccinated HCWs, and we measure the interval from the second vaccine to acquiring the infection.

METHODS

A multicenter retrospective cohort study was conducted in different regions at (16) Ministry of Defense Health Services (MODHS) hospitals. Data were restricted to fully vaccinated (minimum of 2 doses) HCWs who had a confirmed positive PCR test and employed in MODHS hospitals from August 2021 to March 2022.

RESULTS

A total of 45862 HCWs were vaccinated as of Aug 2021. Of these 1253 participants met the selection criteria and were included in the study. The average age of infected HCWs was 35.27 years (SD = ± 8.10) of which 57% were females. The HCWs were employed as doctors (24%), nurses (33%), and other (43%). The most administered vaccine type was mRNA (44%) followed by Adenovirus Viral Vector (39%) and mixed vaccine (17%). The incidence of COVID-19 vaccine breakthrough (BT) infection among HCWs was observed at 2.73% (m-RNA 3.19%, Viral Vector 2.83% and mixed 1.87%).

CONCLUSION

the overall COVID-19 (BT) infection incidence proportion was (2.73%), with the Mixed vaccine group showing the lowest (BT) incidence proportion (1.87%). The most commonly reported symptoms among (BT) infections were cough (51%), sore throat (51%), fever (47%), headache (31%), and runny nose (23%), with overall (6%) asymptomatic (BT) infections. We had (1%) hospital admissions, Zero ICU admission, and Zero deaths. our finding may indicate that infection affecting fully vaccinated patients were less severe and mostly affected the upper respiratory tract.

Durability of the Effectiveness of Heterologous COVID-19 Vaccine Regimens in Thailand: Retrospective Cohort Study Using National Registration Data

BACKGROUND

The durability of heterologous COVID-19 vaccine effectiveness (VE) has been primarily studied in high-income countries, while evaluation of heterologous vaccine policies in low- and middle-income countries remains limited.

OBJECTIVE

We aimed to evaluate the duration during which the VE of heterologous COVID-19 vaccine regimens in mitigating serious outcomes, specifically severe COVID-19 and death following hospitalization with COVID-19, remains over 50%.

METHODS

We formed a dynamic cohort by linking records of Thai citizens aged ≥18 years from citizen vital, COVID-19 vaccine, and COVID-19 cases registry databases between May 2021 and July 2022. Encrypted citizen identification numbers were used to merge the data between the databases. This study focuses on 8 common heterologous vaccine sequences: CoronaVac/ChAdOx1, ChAdOx1/BNT162b2, CoronaVac/CoronaVac/ChAdOx1, CoronaVac/ChAdOx1/ChAdOx1, CoronaVac/ChAdOx1/BNT162b2, BBIBP-CorV/BBIBP-CorV/BNT162b2, ChAdOx1/ChAdOx1/BNT162b2, and ChAdOx1/ChAdOx1/mRNA-1273. Nonimmunized individuals were considered for comparisons. The cohort was stratified according to the vaccination status, age, sex, province location, month of vaccination, and outcome. Data analysis employed logistic regression to determine the VE, accounting for potential confounders and durability over time, with data observed over a follow-up period of 7 months.

RESULTS

This study includes 52,580,841 individuals, with approximately 17,907,215 and 17,190,975 receiving 2- and 3-dose common heterologous vaccines (not mutually exclusive), respectively. The 2-dose heterologous vaccinations offered approximately 50% VE against severe COVID-19 and death following hospitalization with COVID-19 for 2 months; however, the protection significantly declined over time. The 3-dose heterologous vaccinations sustained over 50% VE against both outcomes for at least 8 months, as determined by logistic regression with durability time-interaction modeling. The vaccine sequence consisting of CoronaVac/CoronaVac/ChAdOx1 demonstrated >80% VE against both outcomes, with no evidence of VE waning. The final monthly measured VE of CoronaVac/CoronaVac/ChAdOx1 against severe COVID-19 and death following hospitalization at 7 months after the last dose was 82% (95% CI 80.3%-84%) and 86.3% (95% CI 83.6%-84%), respectively.

CONCLUSIONS

In Thailand, within a 7-month observation period, the 2-dose regimens could not maintain a 50% VE against severe and fatal COVID-19 for over 2 months, but all of the 3-dose regimens did. The CoronaVac/CoronaVac/ChAdOx1 regimen showed the best protective effect against severe and fatal COVID-19. The estimated durability of 50% VE for at least 8 months across all 3-dose heterologous COVID-19 vaccine regimens supports the adoption of heterologous prime-boost vaccination strategies, with a primary series of inactivated virus vaccine and boosting with either a viral vector or an mRNA vaccine, to prevent similar pandemics in low- and middle-income countries.

Long-Term Dynamic Changes in Hybrid Immunity over Six Months after Inactivated and Adenoviral Vector Vaccination in Individuals with Previous SARS-CoV-2 Infection

Numerous studies have largely focused on short-term immunogenicity in recovered individuals post mRNA vaccination. However, understanding the long-term durability, particularly in inactivated and adenoviral vectored vaccines, remains limited. We evaluated antibody responses, omicron variant neutralization, and IFN-γ responses in 119 previously infected individuals vaccinated with CoronaVac or ChAdOx1 up to six months post-vaccination. Both vaccines elicited robust immune responses in recovered individuals, surpassing those who were infection-naïve, and these persisted above pre-vaccination levels for six months. However, antibody levels declined over time (geometric mean ratio (GMR) = 0.52 for both vaccines). Notably, neutralizing activities against omicron declined faster in ChAdOx1 (GMR = 0.6) compared to CoronaVac recipients (GMR = 1.03). While the first dose of ChAdOx1 adequately induced immune responses in recovered individuals, a second dose demonstrated advantages in omicron variant neutralization and slower decline. Although both vaccines induced T cell responses, the median IFN-γ level at six months returned to pre-vaccination levels. However, more individuals exhibited reactive T cell responses. Extending the interval (13-15 months) between infection and vaccination could enhance antibody levels and broaden neutralization. Together, these findings demonstrate a robust humoral and cellular response that was sustained for at least six months after vaccination, thus guiding optimal vaccination strategies based on prior infection and vaccine platforms.

Immunogenicity and safety of heterologous versus homologous prime-boost schedules with inactivated and adenoviral vectored SARS-CoV-2 vaccines - A prospective multi-center study

Background

During the peak of Coronavirus disease (COVID-19) pandemic in Thailand when the emergence of delta variant reduced the efficacy of inactivated vaccine, Thailand had abundance of inactivated vaccine but mRNA vaccine was not available and the supply of adenoviral-vectored vaccine was limited. The heterologous vaccination using CoronaVac and ChAdOx1-nCoV-19 vaccines was applied. We aim to compare the immunogenicity of immune response of primary vaccination with homologous ChAdOx1 nCoV-19 and heterologous vaccination with CoronaVac and ChAdOx1 nCoV-19.

Methods

A total of 430 adults, scheduled to receive ChAdOx1-nCoV-19 as their second dose of primary COVID-19 vaccination, were enrolled. Participants were classified into two groups based on the first dose vaccine as CoronaVac (heterologous group) or ChAdOx1 nCoV-19 (homologous group). The primary outcome was antibodies to the SARS-CoV-2 spike protein receptor binding domain (anti-RBD) titres at 28 days after the second dose of vaccination. Secondary outcomes were anti-RBD titres at 90 days, surrogate viral neutralizing test (sVNT) at 28 and 90 days, and adverse events.

Findings

In 358 participants with correct vaccine interval, the anti-RBD geometric mean titre ratio for the heterologous versus homologous group was 0.55 (95%CI; 0.44-0.067); p < 0.001 at day 28, and 0.80 (95%CI; 0.65-1.00); P = 0.05 at day 90. Median sVNT neutralizing activity was not significantly different in the heterologous versus homologous group at 28 days (93.5 vs 92.7 %); p = 0.13, but significantly higher in the heterologous group at day 90 (82.9 vs 76.4 %); p = 0.01.

Interpretation

The homologous vaccination resulted in higher anti-RBD titres at 28 days after vaccination, but titres in the homologous group showed more rapid decline at 90 days. In the sVNT assay, median neutralization was similar at 28 days, but was longer-lasting and higher in the heterologous group at 90 days.

Funding

This research received funding from the Royal College of Physicians of Thailand special grant 2021 for research initiative during COVID-19 pandemic.

Durability of immune response against omicron BA.2 and BA.4/5 and T cell responses after boosting with mRNA and adenoviral vector-based vaccines following heterologous CoronaVac/ChAdOx-1nCov-19 vaccination

Heterologous vaccination with inactivated vaccine followed by adenoviral vector-based vaccine has shown superiority in enhancing immune response compared to homologous primary series. However, data comparing immunity decline after a third booster following heterologous CoronaVac/ChAdOx-1nCov-19 has been limited. Here, we assessed neutralizing activity against omicron variant and T cell response at 3 months monitoring in 96 individuals who received ChAdOx-1nCov-19, BNT162b2, or mRNA-1273 as a third dose following heterologous CoronaVac/ChAdOx-1nCov-19. Comparing the antibody levels at 3 and 1 month(s) after the third booster, the results showed a persistence of anti-RBD IgG in all vaccine regimens, with the IgG level waning slower in the ChAdOx-1nCov-19 boosted group (geometric mean ratio (GMR): 0.64 (95%CI: 0.59-0.70)) compared to the BNT162b2 (0.34 (95%CI:0.31-0.38)) and mRNA-1273 boosted groups (0.32 (95%CI: 0.29-0.36)). Neutralizing activity against omicron BA.2 and BA.4/5 dropped by 1.2 to 1.5-fold but remained detectable, with the highest level observed in the mRNA-1273 group, followed by BNT162b2 and ChAdOx-1nCov-19 groups, respectively. Furthermore, the number of individuals with T cell reactivity decreased in BNT162b2 and mRNA-1273 groups, while it increased in ChAdOx-1nCov-19 group at 3-month post-boost compared to 1 month. Data on the durability of immune response could help comprehensively optimize the booster vaccine strategy.

Modeling vaccination strategies with limited early COVID-19 vaccine access in low- and middle-income countries: A case study of Thailand

Low- and middle-income countries faced significant challenges in accessing COVID-19 vaccines during the early stages of the pandemic. In this study, we utilized an age-structured modeling approach to examine the implications of various vaccination strategies, vaccine prioritization, and vaccine rollout speeds in Thailand, an upper-middle-income country experiencing vaccine shortages during the early stages of the pandemic. The model directly compares the effectiveness of several vaccination strategies, including the heterologous vaccination where CoronaVac (CV) vaccine was administered as the first dose, followed by ChAdOx1 nCoV-19 (AZ) vaccine as the second dose, under varying disease transmission dynamics. We found that the traditional AZ homologous vaccination was more effective than the CV homologous vaccination, regardless of disease transmission dynamics. However, combining CV and AZ vaccines via either parallel homologous or heterologous vaccinations was more effective than relying solely on AZ homologous vaccination. Additionally, prioritizing vaccination for the elderly aged 60 years and above was the most effective way to reduce mortality when community transmission is well-controlled. On the other hand, prioritizing workers aged 20-59 was most effective in lowering COVID-19 cases, irrespective of the transmission dynamics. Lastly, despite the vaccine prioritization strategy, rapid vaccine rollout speeds were crucial in reducing COVID-19 infections and deaths. These findings suggested that in low- and middle-income countries where early access to high-efficacy vaccines might be limited, obtaining any accessible vaccines as early as possible and using them in parallel with other higher-efficacy vaccines might be a better strategy than waiting for and relying solely on higher-efficacy vaccines.

Sex Differences in Serious Adverse Events Reported Following Booster Doses of COVID-19 Vaccination in Thailand: A Countrywide Nested Unmatched Case-Control Study

A booster dose of a COVID-19 vaccine has been proven effective in restoring vaccine effectiveness and is currently recommended for use in some populations at risk of severe COVID-19 infection. Since sex differences in adverse events are significant in response to the vaccines, the safety of booster selection must be studied to avoid serious adverse events (SAE), such as life-threatening diseases. First, this study aimed to identify sex differences in SAE incidences using a prospective cohort design. Second, a nested unmatched case-control study was used to identify factors associated with reported SAE within 30 days after the booster shot. Multivariable logistic regression indicated the adjusted odds ratio by accounting for host and vaccine variables, thus, policy effects. The findings confirmed that SAE was rare and that age-sex-dominated disease classifications differed. Specific to SAE following the booster dose, we found that females aged 12-40 had a higher risk of being reported with SAE than males of the same age, while males over 50 had a higher risk than females. Other risk factors identified were the presence of metabolic syndrome and the use of certain vaccine brands. Mechanisms could be explained by individual host responses rather than the vaccines' direct effect. Therefore, SAE could be preventable by age-sex-specific vaccine selection, post-vaccination precautions, and early symptom detection. Future vaccine development should aim to limit host-specific reactogenicity for safety concerns.

Safety and immunogenicity of the third and fourth doses of vaccine against SARS-CoV-2 following a 2-dose regimen of inactivated whole-virion SARS-CoV-2 vaccine

This study followed healthcare personnel (HCP) who had completed a primary series of CoronaVac and then received the third and fourth doses of COVID-19 vaccine. The primary objective was to determine the seroconversion rate of neutralizing antibodies against wild-type SARS-CoV-2 and VOCs at day 28 after the third dose of vaccine and day 28 after the fourth dose of vaccine. This prospective cohort study was conducted at Maharaj Nakorn Chiang Mai Hospital, a tertiary care hospital affiliated to Chiang Mai University from July 2021 to February 2022. Two hundred and eighty-three participants were assessed for eligibility; 142 had received AZD1222 and 141 BNT162b2 as the third dose. Seroconversion rates using a 30% inhibition cutoff value against wild-type SARS-CoV-2 were 57.2%, 98.6%, 97.8%, and 98.9% at points before and after the third dose, before and after the fourth dose, respectively among those receiving AZD1222 as the third dose. Frequencies were 31.9%, 99.3%, 98.9%, and 100% among those receiving BNT162b2 as the third dose, respectively. The seroconversion rates against B.1.1.529 [Omicron] were 76.1% and 90.2% (p-value 0.010) at 4 weeks after the third dose in those receiving AZD1222 and BNT162b2 as the third dose, respectively. After a booster with the mRNA vaccine, the seroconversion rates increased from 21.7 to 91.3% and from 30.4 to 91.3% in those receiving AZD1222 and BNT162b2 as the third dose, respectively. No serious safety concerns were found in this study. In conclusion, antibody responses waned over time regardless of the vaccine regimen. The booster dose of the vaccine elicited a humoral immune response against SARS-CoV-2 including SARS-CoV-2 variants of concern, including B.1.1.529 [Omicron], which was circulating during the study period. However, the results might not be extrapolated to other Omicron sublineages.

Neutralizing antibody and T-cell responses against SARS-CoV-2 variants by heterologous CoronaVac/ChAdOx-1 vaccination in elderly subjects with chronic obstructive pulmonary disease

BACKGROUND

Data on humoral and cellular immune responses against SARS-CoV-2 after receiving heterologous CoronaVac/ChAdOx-1 (CoVac/ChAd) vaccination in subjects with chronic obstructive pulmonary disease (COPD) are still limited. Therefore, we determined the neutralizing antibody (NAb) and T-cell responses against SARS-CoV-2 wild type (WT) and variants of concern (VOCs) in COPD patients.

METHODS

The levels of NAb as well as specific CD4 and CD8 T-cell responses against SARS-CoV-2 WT and VOCs were determined in COPD patients before and after vaccination.

RESULTS

Four weeks after vaccinations, the median levels of % inhibition of NAb against SARS-CoV-2 WT, Alpha, Beta, and Delta variants were significantly higher compared to pre-vaccination. The induction of NAb against Omicron was very low compared to other variants. At four weeks after vaccination, in comparison to pre-vaccination, the increasing trend of TNF-α-, IFN-γ-, IL-4-, IL-17-, IL-10-, and FasL-producing CD4 T-cells upon stimulation with WT spike peptides were demonstrated. No difference in T-cell responses to spike peptides of Alpha, Beta, and Delta variants and their WT homologs was observed.

CONCLUSION

Heterologous CoVac/ChAd vaccine induced the production of NAb against SARS-CoV-2 WT, Alpha, Beta, and Delta variants, but low for Omicron in COPD patients. Induction of CD4 T-cell subset responses was slightly observed by this vaccine regimen.

CLINICAL TRIALS REGISTRY

This study was approved by the Clinical Trials Registry (Study ID: TCTR20210822002).

Comparative Safety and Effectiveness of Heterologous CoronaVac-ChAdOx1 versus Homologous CoronaVac Vaccination in a Real-World Setting: A Retrospective Cohort Study

Background: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has outpaced vaccine availability and delivery from vaccine manufacturers, and thus, a scarcity of vaccines happened to many countries around the world. In Thailand, the mixing of different types of vaccines was approved and clinically implemented partially due to concerns about the availability and efficacy of one vaccine. Objective: This study aimed to investigate the effectiveness and safety of heterologous CoronaVac-ChAdOx1 nCoV-19 vaccines compared with the usual regimen of homologous CoronaVac-CoronaVac. A retrospective cohort study was conducted by dividing patients into the CoronaVac-CoronaVac group and the CoronaVac-ChAdOx1 group. Results: A total of 875 patients received vaccinations at Srisangwan Hospital between April to October 2021 and were included for analysis. The patients in both homologous and heterologous groups had low rates of COVID-19 infection. In addition, the hospitalization rates in the 40 days after the second vaccination were low in both regimens. Minimal adverse events (AE) were reported in both groups, including local AE (e.g., discomfort at the injection site, rash, soreness, swelling, and redness) and systemic AE (e.g., fever, headache, weariness, nausea, vomiting, diarrhoea, and myalgia). Moreover, several factors were associated with lower adverse events following immunization (AEFIs), including age ≥ 50 years, male, and body weight ≥ 50 kg. In contrast, thyroid disease, diabetes mellitus, allergic rhinitis, and psychiatric disorders were independent risk factors associated with an increase in AEFIs. Conclusions: The heterologous CoronaVac-ChAdOx1 and homologous CoronaVac-CoronaVac regimens were promising vaccination strategies for the prevention of SARS-CoV-2 infection. However, the heterologous CoronaVac-ChAdOx1 potentially caused fewer AEFIs compared with the homologous CoronaVac-CoronaVac regimen.

Heterologous COVID-19 Vaccination and Booster with mRNA Vaccine Provide Enhanced Immune Response in Patients with Cirrhosis: A Prospective Observational Study

This study aimed to evaluate the antibody and cellular responses to different coronavirus 2019 (COVID-19) vaccination regimens in patients with cirrhosis and to assess the antibody response after a vaccine booster. We conducted a prospective observational study of 89 patients with cirrhosis and 41 healthy volunteers who received two COVID-19 vaccine doses. Next, we prospectively evaluated 24 patients with cirrhosis who received a booster COVID-19 vaccine dose. In both studies, blood samples were collected before and 4 weeks after vaccination, and anti-spike receptor-binding domain protein IgG levels, T-cell phenotypes, and effector functions were assessed. The heterologous vaccine regimen (CoronaVac [SV]/AstraZeneca [AZ]) produced a better antibody response and CD4+IFNg+ T cell response compared to homogeneous vaccine regimens. The antibody response after the second dose of the vaccine was similar in patients with cirrhosis and healthy volunteers. Patients who received a booster dose of the mRNA vaccine had significantly increased antibody titers compared to those who received the AZ vaccine. In patients with cirrhosis, heterologous vaccination with SV/AZ resulted in a better immune response than the AZ/AZ and SV/SV regimens. Moreover, a booster dose of the mRNA vaccine led to a greater increase in antibody titers compared to the AZ vaccine.

Dynamic Antibody Response and Hybrid Immunity Following Multiple COVID-19 Vaccine Doses and Infection: A Case Study

This case study highlights the dynamic nature of the antibody response to SARS-CoV-2 in a vulnerable subject aged 70 years between 2021 and 2023. This individual had been vaccinated with six doses of the ancestral (Wuhan-Hu-1) COVID-19 vaccine and had a breakthrough infection 126 days after receiving Covovax™- (CO) as the sixth dose. The serostatus for total immunoglobulin specific to the receptor binding domain (total RBD Ig) changed from negative to positive following a two-dose CoronaVac (CV) vaccination, indicating a successful immune response. Booster doses, including AZD1222 (AZ), half-dose BNT162b2 (PF), and CO, increased the total RBD Ig levels, except for CV. The individual experienced a breakthrough infection by the Omicron BA.5 variant, leading to a substantial surge in total RBD Ig to over 105 U/mL. This generated sustained and extended antibody persistence, with the half-life of total RBD Ig lasting approximately 103.6 days. Furthermore, it has been observed that this breakthrough infection generated the highest neutralizing antibodies against BA.5, followed by XBB.1.5, BQ.1.1, and BA.2.75, respectively.

Anti-SARS-CoV-2 receptor binding domain antibodies after the second dose of Sinovac and AstraZeneca vaccination

Purpose

The Sinovac and AstraZeneca vaccines are the primary coronavirus disease 2019 vaccines in Indonesia. Antibody levels in vaccine-injected individuals will decline substantially over time, but data supporting the duration of such responses are limited. Therefore, this study aims to quantitatively evaluate antibody responses resulting from the completion of Sinovac and AstraZeneca administration in Indonesian adults.

Materials and Methods

Participants were divided into two groups based on their vaccine type. Both groups were then assessed on the anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) receptor binding domain (anti-SRBD) concentrations. The anti-SRBD level was measured using Elecsys anti-SARS-CoV-2 S assay and analyzed every month until 3 months after the second vaccination.

Results

The results presented significant differences (p=0.000) in immunoglobulin G (IgG) titers among the vaccines' measurement duration, where all samples observed a decrease in IgG titers over time. The mean titer levels of anti-SRBD IgG in the group given Sinovac were high in the first month after vaccination and decreased by 55.7% in 3 months. AstraZeneca showed lesser immune response with a slower decline rate. Adverse effects following immunization (AEFI) showed that systemic reactions are the most reported in both vaccines, with a higher percentage in the second dose of AstraZeneca type vaccines.

Conclusion

Sinovac induced more significant titers of anti-SRBD IgG 1 month after the second dose but generated fewer AEFIs. In contrast, AstraZeneca generated more AEFIs, in mild to moderate severity, but provided lower levels of anti-SRBD IgG.

SARS-CoV-2 Antibody Dynamics after COVID-19 Vaccination and Infection: A Real-World Cross-Sectional Analysis

The Coronavirus disease 2019 (COVID-19) pandemic, caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), continues to surge despite the widespread use of vaccination. In Thailand, more than 77% and 39% of the population received two doses and three doses of COVID-19 vaccines as of December 2022, respectively. In addition, during the Omicron predominant period in 2022, more than 70% of Thai individuals have been infected. To gain comprehensive insight into SARS-CoV-2 antibody dynamics following vaccination or following vaccination and infection (hybrid immunity), we performed a cross-sectional analysis of sera samples from individuals who received COVID-19 vaccination and/or have been infected with COVID-19 in Thailand between January 2021 and December 2022. A total of 4126 samples were collected. Humoral immunity was evaluated by quantifying the immunoglobulin (including IgG, IgM, and IgA isotypes) specific to the SARS-CoV-2 receptor-binding domain (RBD) or Ig anti-RBD. The results showed that individuals who received two-dose vaccination alone had lower levels of Ig anti-RBD, which rapidly waned over time. To restore the waning antibody, a third dose vaccination is recommended for uninfected individuals who have only received 2 doses.

Characterization of immune responses to two and three doses of the adenoviral vectored vaccine ChAdOx1 nCov-19 and the whole virion inactivated vaccine BBV152 in a mix-and-match study in India

Infections with SARS-CoV-2 variants and declining immunity after primary vaccination, encouraged the use of booster doses. Some countries changed their immunization programmes to boost with vaccines different from the ones in their original schedule, based on results from immunogenicity and effectiveness studies. This study reports immunological analysis of samples collected in a phase 4 randomized trial, where participants who had previously received two primary doses of ChAdOx1 nCov-19 (ChAd) or inactivated BBV152 vaccine were randomized to receive either ChAd or BBV152 booster and further categorized as: Group 1 (two primary doses of ChAd - ChAd booster), Group 2 (two primary doses of ChAd - BBV152 booster), Group 3 (two primary doses of BBV152 - ChAd booster), and Group 4 (two primary doses of BBV152 - BBV152 booster). SARS-CoV-2 specific cellular and humoral responses at day 0 (pre-boost samples 12-36 weeks after the second primary dose), and at day 28 post booster, were measured in a subset of participants (ChAd recipients, n = 37 and BBV152 recipients, n = 36). Additionally, on day180 post-booster humoral responses were assessed for the entire cohort (N = 378). Primary vaccination with 2 doses of BBV152 generated higher memory-B cells (median% 0.41 vs 0.35) and cytokine producing CD8-Tcells (median% 0.09 vs 0.04) while lower anti-spike IgG levels (medianAU/ml: 12,433 vs 27,074) as compared to ChAd. Irrespective of the primary vaccine received, ChAd boosted individuals generated higher memory-B cell frequencies and anti-spike IgG levels as compared to BBV152 booster. The percentage ACE-2 inhibition against Omicron and its sub-variants was higher in Group 3 (median > 60 %) as compared to other groups (median < 25 %). At day180 post booster the hierarchy of the antibody amounts was Group 1 ∼ Group 2 ∼ Group 3 > Group 4. Sustained humoral and robust cellular immune response to SARS-CoV-2 can be obtained with ChAd booster irrespective of the primary vaccination regimen. The trial is registered with ISRTCN (CTRI/2021/08/035648).

Safety and Immunogenicity of Homologous and Heterologous Adenoviral-Vectored and mRNA COVID-19 Vaccine Regimens in Radiotherapy Patients

Diminished immune response after vaccination occurs in cancer patients. This observational study evaluated the immune response and safety profile after COVID-19 vaccination in radiotherapy patients. The study comprised 53 cancer patients undergoing radiotherapy and voluntarily received the COVID-19 vaccine. The two regimens were homologous ChAdOx1-S recombinant (AstraZeneca, AZ), "AZ-AZ" and heterologous "AZ-mRNA". The seroconversion rate and anti-RBD immunoglobulin geometric mean titers (GMT) were assessed and compared with healthy controls. Adverse effects were assessed using a questionnaire. The seroconversion rate was 52.4% 1 month after the first dose with GMT 4.3 U/mL (95%CI 1.4-13). Following the second dose, the AZ-AZ group achieved 95% seroconversion rate with GMT = 188.4 U/mL (95%CI 67.1-529), which was significantly lower than the healthy cohort, GMT = 945 U/mL (95%CI 708-1261). Cancer patients in AZ-mRNA group achieved a 100% seroconversion rate with a high GMT = 1400.8 U/mL (95%CI 429.5-4566), which was significantly lower than the healthy cohort, GMT = 5169.9 U/mL (95%CI 3582.2-7461.5). Most adverse effects were mild. Our findings suggest that radiotherapy patients had fair immunogenicity after the first dose, but achieved a high seroconversion rate after the second dose with manageable adverse effects. However, their immunologic response was lower than in healthy individuals, indicating that other preventive strategies are needed.

Evaluation of Anti-S1 IgA Response to Different COVID-19 Vaccination Regimens

IgA plays a crucial role in early virus neutralization. To identify the IgA stimulation by COVID-19 vaccine, this study aimed to evaluate the level of anti-S1 IgA in the serum of participants immunized with different COVID-19 vaccination regimens. Sera from 567 eligible participants vaccinated with two, three, or four doses of different types of COVID-19 vaccine were recruited. Post-vaccine anti-S1 IgA responses significantly varied according to vaccine type and regimen. The finding showed that heterologous boosters, especially after priming with an inactivated vaccine, elicited higher IgA levels than homologous boosters. Vaccination with SV/SV/PF produced the highest IgA level among all the immunization regimens after either two, three, or four doses. The different routes and amounts of vaccine used for vaccination showed non-significant differences in IgA levels. After the third dose of immunization for 4 months, the level of IgA decreased significantly from the level found on day 28 in both SV/SV/AZ and SV/SV/PF groups. In conclusion, our study showed that heterologous booster regimens for COVID-19 elicited higher anti-S1 IgA levels in serum, especially after priming with inactivated vaccine. The presented anti-S1 IgA may have advantages in preventing SARS-CoV-2 infection and severe disease.

Immunogenicity and reactogenicity of heterologous prime-boost vaccination with inactivated COVID-19 and ChAdOx1 nCoV-19 (AZD1222) vaccines, a quasi-experimental study

The global supply of COVID-19 vaccines has been limited, and concerns have arisen about vaccine supply chain disruptions in developing countries. Heterologous prime-boost vaccination, which involves using different vaccines for the first and second doses, has been proposed to enhance the immune response. We aimed to compare the immunogenicity and safety of a heterologous prime-boost vaccination using an inactivated COVID-19 vaccine and AZD1222 vaccine with that of a homologous vaccination using AZD1222. This pilot involved 164 healthy volunteers without prior SARS-CoV-2 infection aged 18 years or older assigned to receive either the heterologous or homologous vaccination. The results showed that the heterologous approach was safe and well-tolerated, although the reactogenicity of the heterologous approach was higher. At 4 weeks after receiving the booster dose, the heterologous approach elicited a non-inferior immune response compared to the homologous approach in neutralizing antibody and cell-mediated immune response. The percentage of inhibition was 83.88 (79.72-88.03) in the heterologous and 79.88 (75.50-84.25) in the homologous group, a mean difference of 4.60 (-1.67-10.88). The geometric mean of interferon-gamma was 1072.53 mIU/mL (799.29-1439.18) in the heterologous group and 867.67 mIU/mL (671.94-1120.40) in the homologous group, a GMR of 1.24 (0.82-1.85). However, the binding antibody test of the heterologous group was inferior to the homologous group. Our findings suggest that the use of heterologous prime-boost vaccination with different types of COVID-19 vaccines is a viable strategy, especially in settings where vaccine supply is limited or where vaccine distribution is challenging.

Comparison of the reactogenicity and immunogenicity between two-dose mRNA COVID-19 vaccine and inactivated COVID-19 vaccine followed by an mRNA vaccine in children aged 5-11 years

To compare the reactogenicity and immunogenicity between the two-dose mRNA COVID-19 vaccine regimen and one or two doses of inactivated vaccine followed by an mRNA vaccine regimen in healthy children between 5 and 11 years of age, a prospective cohort study was performed at King Chulalongkorn Memorial Hospital in Thailand between March to June 2022. Healthy children between 5 and 11 years of age were enrolled and received the two-dose mRNA COVID-19 vaccine (BNT162b2) regimen or the inactivated (CoronaVac) vaccine followed by the BNT162b2 vaccine regimen. In addition, healthy children who received two doses of BBIBP-CorV between 1 and 3 months prior were enrolled to receive a heterologous BNT162b2 as a third dose (booster). Reactogenicity was assessed by a self-reported online questionnaire. Immunogenicity analysis was performed to determine binding antibodies to wild-type SARS-CoV-2. Neutralizing antibodies to Omicron variants (BA.2 and BA.5) were tested using the focus reduction neutralization test. Overall, 166 eligible children were enrolled. Local and systemic adverse events which occurred within 7 days after vaccination were mild to moderate and well-tolerated. The two-dose BNT162b2, CoronaVac followed by BNT162b2, and two-dose BBIBP-CorV followed by BNT162b2 groups elicited similar levels of anti-receptor-binding domain (RBD) IgG. However, the two-dose BNT162b2 and two-dose BBIBP-CorV followed by BNT162b2 groups elicited higher neutralizing activities against the Omicron BA.2 and BA.5 variant than the CoronaVac followed by BNT162b2 group. The CoronaVac followed by BNT162b2 group elicited low neutralizing activities against the Omicron BA.2 and BA.5 variant. A third dose (booster) mRNA vaccine should be prioritized for this group.

Sequential Administration of SARS-CoV-2 Strains-Based Vaccines Effectively Induces Potent Immune Responses against Previously Unexposed Omicron Strain

In the past few years, the continuous pandemic of COVID-19 caused by SARS-CoV-2 has placed a huge burden on public health. In order to effectively deal with the emergence of new SARS-CoV-2 variants, it becomes meaningful to further enhance the immune responses of individuals who have completed the first-generation vaccination. To understand whether sequential administration using different variant sequence-based inactivated vaccines could induce better immunity against the forthcoming variants, we tried five inactivated vaccine combinations in a mouse model and compared their immune responses. Our results showed that the sequential strategies have a significant advantage over homologous immunization by inducing robust antigen-specific T cell immune responses in the early stages of immunization. Furthermore, the three-dose vaccination strategies in our research elicited better neutralizing antibody responses against the BA.2 Omicron strain. These data provide scientific clues for finding the optimal strategy within the existing vaccine platform in generating cross-immunity against multiple variants including previously unexposed strains.

Heterologous Vector-mRNA Based SARS-CoV-2 Vaccination Strategy Appears Superior to a Homologous Vector-Based Vaccination Scheme in German Healthcare Workers Regarding Humoral SARS-CoV-2 Response Indicating a High Boosting Effect by mRNA Vaccines

BACKGROUND

Longitudinal humoral SARS-CoV-2 (severe acute respiratory syndrome coronavirus type 2) immunity for up to 15 months due to vaccination, the efficacy of vaccination strategies (homologous, vector-vector versus heterologous, vector-mRNA), the influence of vaccination side effects, and the infection rate in German healthcare workers need to be investigated.

METHODS

In this study, 103 individuals vaccinated against SARS-CoV-2 were enrolled to examine their anti-SARS-CoV-2 anti-N- and anti-RBD/S1-Ig levels. A total of 415 blood samples in lithium heparin tubes were prospectively obtained, and a structured survey regarding medical history, type of vaccine, and vaccination reactions was conducted.

RESULTS

All participants demonstrated a humoral immune response, among whom no values decreased below the positivity cutoff. Five to six months after the third vaccination, three participants showed anti-RBD/S1 antibodies of less than 1000 U/mL. We observed higher levels for heterologous mRNA-/vector-based combinations compared to pure vector-based vaccination after the second vaccination, which is harmonized after a third vaccination with the mRNA-vaccine only in both cohorts. The incidence of vaccine breakthrough in a highly exposed cohort was 60.3%.

CONCLUSION

Sustained long-term humoral immunity was observed, indicating the superiority of a heterologous mRNA-/vector-based combination compared to pure vector-based vaccination. There was longevity of anti-RBD/S1 antibodies of at least 4 and up to 7 months without external stimulus. Regarding vaccination reactogenity, the occurrence of local symptoms as pain at the injection site was increased after the first mRNA application compared to the vector-vector cohort with a general decrease in adverse events at later vaccination time points. Overall, a correlation between the humoral vaccination response and vaccination side effects was not observed. Despite the high prevalence of vaccine breakthroughs, these only occurred in the later course of the study when more infectious variants, which are, however, associated with milder courses, were present. These results provide insights into vaccine-related serologic responses, and the study should be expanded using additional vaccine doses and novel variants in the future.

Comparison of Immunogenicity and Reactogenicity of Five Primary Series of COVID-19 Vaccine Regimens against Circulating SARS-CoV-2 Variants of Concern among Healthy Thai Populations

To compare immunogenicity and reactogenicity of five COVID-19 vaccine regimens against wild-type SARS-CoV-2 and variants of concern (VoCs) among Thai populations, a prospective cohort study was conducted among healthy participants aged ≥18 years who had never been infected with COVID-19 and were scheduled to get one of the five primary series of COVID-19 vaccine regimens, including CoronaVac/CoronaVac, AZD1222/AZD1222, CoronaVac/AZD1222, AZD1222/BNT162b2, and BNT162b2/BNT162b2. Anti-receptor binding domain (anti-RBD-WT) IgG and neutralizing antibody (NAb-WT) against wild-type SARS-CoV-2 were measured at pre-prime, post-prime, and post-boost visits. NAb against VoCs (NAb-Alpha, NAb-Beta, NAb-Delta, and NAb-Omicron) were assessed at the post-boost visit. Adverse events (AEs) following vaccination were recorded. A total of 901 participants (CoronaVac/CoronaVac: 332, AZD1222/AZD1222: 221, CoronaVac/AZD1222: 110, AZD1222/BNT162b2: 128, and BNT162b2/BNT162b2: 110) were enrolled. Anti-RBD-WT IgG and NAb-WT levels increased substantially after each vaccine dose. At the post-boost visit, BNT162b2/BNT162b2 induced the highest GMC of anti-RBD-WT IgG level (1698 BAU/mL), whereas AZD1222/BNT162b2 induced the highest median NAb-WT level (99% inhibition). NAb levels against VoCs, particularly the Omicron strain, were markedly attenuated for all vaccine regimens (p < 0.001). Overall, no serious AEs following vaccination were observed. All five primary series of COVID-19 vaccine regimens were well-tolerated and elicited robust antibody responses against wild-type SARS-CoV-2 but had attenuated responses against VoCs, particularly the Omicron strain, among healthy Thai populations.

Placental Transfer Immunity to the Newborns in a Twin Pregnant Women Vaccinated with Heterologous CoronaVac-ChAdOx1

Pregnant women who receive the COVID-19 vaccine develop anti-SARS-CoV-2 antibodies, which can be transferred to the fetus. However, the effectiveness of placental transfer has not been evaluated in twin pregnancy, especially in cases vaccinated with heterologous CoronaVac (Sinovac)-ChAdOx1 (Oxford-AstraZeneca) regimen, which was commonly used in many countries. Case: A 34-year-old Thai woman with a twin pregnancy attended our antenatal care clinic at 21 + 2 weeks of gestation and requested COVID-19 vaccination. Her medical history and physical examination were unremarkable. She had not received COVID-19 vaccination before. Ultrasound screening for fetal anomaly revealed a dichorion diamnion twin pregnancy. Both twins showed no structural anomaly. She received the CoronaVac vaccine at 21 + 2 weeks of gestation without serious side effects and the ChAdOx1 vaccine at 24 + 2 weeks of gestation. Cesarean delivery was performed at 36 + 5 weeks of gestation, giving birth to the two healthy babies. The levels of anti-spike protein IgG levels (BAU/mL) in maternal blood just before delivery and umbilical cord blood of the two newborns were 313.349, 678.219, and 874.853, respectively. The levels of % inhibition (wild-type and delta) in the two newborns were also higher than those in the mother. In conclusion, heterologous CoronaVac-ChAdOx1-S vaccination in a twin pregnancy could effectively provide protective immunity to both twin newborns. The antibody levels in both were approximately two times higher than those in the mothers. This case report may serve as a reference in counseling couples with a twin pregnancy, while the studies on placental transfer of vaccine-derived antibodies in twin pregnancy are currently not available, especially in countries experiencing a vaccine shortage or unavailability of mRNA vaccines.

A systematic review and meta-analysis of the effectiveness and safety of COVID-19 vaccination in older adults

In the coronavirus disease 2019 (COVID-19) pandemic, vaccinations were essential in preventing COVID-19 infections and related mortality in older adults. The objectives of this study were to evaluate the effectiveness and safety of the COVID-19 vaccines in older adults. We systematically searched the electronic bibliographic databases of PubMed, Web of Science, Embase, Cochrane Library, ClinicalTrials.gov, Research Square, and OpenGrey, as well as other sources of gray literature, for studies published between January 1, 2020, and October 1, 2022. We retrieved 22 randomized controlled trials (RCTs), with a total of 3,404,696 older adults (aged over 60 years) participating, that were included in the meta-analysis. No significant publication bias was found. In the cumulative meta-analysis, we found that the COVID-19 vaccines were effective in preventing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (OR = 0.38, 95% CI = 0.23-0.65, p = 0.0004) and in reducing the number of COVID-19-related deaths (OR = 0.16, 95% CI = 0.10-0.25, p < 0.00001) in elderly people. Antibody seroconversion (AS) and geometric mean titer (GMT) levels significantly increased in vaccinated older adults [OR = 24.42, 95% CI = 19.29-30.92; standardized mean difference (SMD) = 0.92, 95% CI = 0.64-1.20, respectively]. However, local and systemic adverse events after COVID-19 vaccine administration were found in older adults (OR = 2.57, 95% CI = 1.83-3.62, p < 0.00001). Although vaccination might induce certain adverse reactions in the elderly population, the available evidence showed that the COVID-19 vaccines are effective and tolerated, as shown by the decrease in COVID-19-related deaths in older adults. It needs to be made abundantly clear to elderly people that the advantages of vaccination far outweigh any potential risks. Therefore, COVID-19 vaccination should be considered as the recommended strategy for the control of this disease by preventing SARS-CoV-2 infection and related deaths in older adults. More RCTs are needed to increase the certainty of the evidence and to verify our conclusions.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022319698, identifier CRD42022319698.

An Immunological Review of SARS-CoV-2 Infection and Vaccine Serology: Innate and Adaptive Responses to mRNA, Adenovirus, Inactivated and Protein Subunit Vaccines

The coronavirus disease 2019 (COVID-19) pandemic is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, which is defined by its positive-sense single-stranded RNA (ssRNA) structure. It is in the order Nidovirales, suborder Coronaviridae, genus Betacoronavirus, and sub-genus Sarbecovirus (lineage B), together with two bat-derived strains with a 96% genomic homology with other bat coronaviruses (BatCoVand RaTG13). Thus far, two Alphacoronavirus strains, HCoV-229E and HCoV-NL63, along with five Betacoronaviruses, HCoV-HKU1, HCoV-OC43, SARS-CoV, MERS-CoV, and SARS-CoV-2, have been recognized as human coronaviruses (HCoVs). SARS-CoV-2 has resulted in more than six million deaths worldwide since late 2019. The appearance of this novel virus is defined by its high and variable transmission rate (RT) and coexisting asymptomatic and symptomatic propagation within and across animal populations, which has a longer-lasting impact. Most current therapeutic methods aim to reduce the severity of COVID-19 hospitalization and virus symptoms, preventing the infection from progressing from acute to chronic in vulnerable populations. Now, pharmacological interventions including vaccines and others exist, with research ongoing. The only ethical approach to developing herd immunity is to develop and provide vaccines and therapeutics that can potentially improve on the innate and adaptive system responses at the same time. Therefore, several vaccines have been developed to provide acquired immunity to SARS-CoV-2 induced COVID-19-disease. The initial evaluations of the COVID-19 vaccines began in around 2020, followed by clinical trials carried out during the pandemic with ongoing population adverse effect monitoring by respective regulatory agencies. Therefore, durability and immunity provided by current vaccines requires further characterization with more extensive available data, as is presented in this paper. When utilized globally, these vaccines may create an unidentified pattern of antibody responses or memory B and T cell responses that need to be further researched, some of which can now be compared within laboratory and population studies here. Several COVID-19 vaccine immunogens have been presented in clinical trials to assess their safety and efficacy, inducing cellular antibody production through cellular B and T cell interactions that protect against infection. This response is defined by virus-specific antibodies (anti-N or anti-S antibodies), with B and T cell characterization undergoing extensive research. In this article, we review four types of contemporary COVID-19 vaccines, comparing their antibody profiles and cellular aspects involved in coronavirus immunology across several population studies.

Immunogenicity, Immune Dynamics, and Subsequent Response to the Booster Dose of Heterologous versus Homologous Prime-Boost Regimens with Adenoviral Vector and mRNA SARS-CoV-2 Vaccine among Liver Transplant Recipients: A Prospective Study

Background: Heterologous prime-boost vaccination potentially augments the immune response against SARS-CoV-2 in liver transplant (LT) recipients. We investigated immunogenicity induced by different primary prime-boost vaccination protocols and the subsequent response to the booster vaccine among LT recipients. Methods: LT recipients, who received primary immunisation with ChAdOx1/ChAdOx1 or ChAdOx1/BNT162b2, were administered the third dose of mRNA-1273 three months following the primary vaccination. Blood samples were collected before and after primary vaccination and post-booster. The levels of receptor binding domain antibody (anti-RBD) and neutralising antibody (sVNT) and spike-specific T-cell responses were assessed. Results: Among the 89 LT recipients, patients receiving ChAdOx1/BNT162b2 had significantly higher anti-RBD titres, sVNT, and cellular response after primary vaccination than those receiving ChAdOx1/ChAdOx1 (p < 0.05). The antibody response decreased 12 weeks after the primary vaccination. After the booster, humoral and cellular responses significantly improved, with comparable seroconversion rates between the heterologous and homologous groups. Positive sVNT against the wild type occurred in >90% of LT patients, with only 12.3% positive against the Omicron variant. Conclusions: ChAdOx1/BNT162b2 evoked a significantly higher immunological response than ChAdOx1/ChAdOx1 in LT recipients. The booster strategy substantially induced robust immunity against wild type in most patients but was less effective against the Omicron strain.

Effects of boosted mRNA and adenoviral-vectored vaccines on immune responses to omicron BA.1 and BA.2 following the heterologous CoronaVac/AZD1222 vaccination

The coronavirus 2019 omicron variant has surged rapidly and raises concerns about immune evasion even in individuals with complete vaccination, because it harbors mutations. Here we examine the capability of booster vaccination following CoronaVac/AZD1222 prime to induce neutralizing antibodies (NAbs) against omicron (BA.1 and BA.2) and T-cell responses. A total of 167 participants primed with heterologous CoronaVac/AZD1222 for 4-5 months were enrolled, to receive AZD1222, BNT162b2, or mRNA-1273 as a third dose. Reactogenicity was recorded. Immunogenicity analyses of severe acute respiratory syndrome coronavirus 2-binding antibodies were measured using enzyme-linked immunosorbent assay. The NAb titers against omicron BA.1 and BA.2 were determined using the focus reduction neutralization test (FRNT50) and total interferon-γ responses were measured to observe the T-cell activation. A substantial loss in neutralizing potency to omicron variant was found at 4-5 months after receiving the heterologous CoronaVac/AZD1222. Following booster vaccination, a significant increase in binding antibodies and neutralizing activities toward delta and omicron variants was observed. Neutralization to omicron BA.1 and BA.2 were comparable, showing the highest titers after boosted mRNA-1273 followed by BNT162b2 and AZD1222. In addition, individuals boosted with messenger RNA (mRNA) vaccines develop a T-cell response to spike protein, whereas those boosted with AZD1222 did not. Reactogenicity was mild to moderate without serious adverse events. Our findings demonstrated that mRNA booster vaccination is able to overcome waning immunity to provide antibodies that neutralize omicron BA.1 and BA.2, as well as a T-cell response.

Vaccine-Related adverse events following AZD1222 (ChAdOx1-nCoV-19) Covid-19 vaccine in solid malignancy patients receiving cancer treatment, as compared to age-matched healthy controls

The study aimed to evaluate vaccine-related adverse events (VRAEs) following ChAdOx1-nCoV-19 vaccine in solid cancer patients receiving treatment compared to healthy controls. 399 cancer patients and 90 healthy volunteers were enrolled. In the overall population, the incidence of VRAEs was significantly lower in cancer patients than in healthy volunteers (57% vs 80%, P < .001). Because the mean age of the cancer patients was higher than the healthy volunteers (59 vs 48 years, P < .001), we analyzed age-matched comparison and found that there was no significant difference of VRAEs between two groups (74% vs 79%, P .32). Most VRAEs were of mild severity in both groups. The most common local VRAE was pain at the injection site in both groups, and the most common systemic VRAE was fatigue in the cancer cohort, while myalgia was the most common VRAE among the healthy controls. In the cancer cohort, fever was the only VRAE that led to interruption of the cancer treatment (in two cases). Among the cancer treatment types, patients undergoing chemotherapy-containing regimens had a lower likelihood of experiencing VRAEs. In summary, the overall incidence of VRAEs following ChAdOx1-nCoV-19 vaccine in actively treated cancer patients was comparable to healthy controls after adjusting for age. The VRAEs that occurred rarely interfered with the cancer treatment. These findings substantiate that vaccination with AZD1222 is safe in cancer patients undergoing treatment.

Immunogenicity and reactogenicity of a third dose of BNT162b2 vaccine for COVID-19 after a primary regimen with BBIBP-CorV or BNT162b2 vaccines in Lima, Peru

BACKGROUND

The administration of a third (booster) dose of COVID-19 vaccines in Peru initially employed the BNT162b2 (Pfizer) mRNA vaccine. The national vaccination program started with healthcare workers (HCW) who received BBIBP-CorV (Sinopharm) vaccine as primary regimen and elderly people previously immunized with BNT162b2. This study evaluated the reactogenicity and immunogenicity of the "booster" dose in these two groups in Lima, Peru.

METHODS

We conducted a prospective cohort study, recruiting participants from November to December of 2021 in Lima, Peru. We evaluated immunogenicity and reactogenicity in HCW and elderly patients previously vaccinated with either two doses of BBIBP-CorV (heterologous regimen) or BTN162b2 (homologous regimen). Immunogenicity was measured by anti-SARS-CoV-2 IgG antibody levels immediately before boosting dose and 14 days later. IgG geometric means (GM) and medians were obtained, and modeled using ANCOVA and quantile regressions.

RESULTS

The GM of IgG levels increased significantly after boosting: from 28.5±5.0 AU/mL up to 486.6±1.2 AU/mL (p<0.001) which corresponds to a 17-fold increase. The heterologous vaccine regimen produced higher GM of post-booster anti-SARS-CoV-2 IgG levels, eliciting a 13% increase in the geometric mean ratio (95%CI: 1.02-1.27) and a median difference of 92.3 AU/ml (95%CI: 24.9-159.7). Both vaccine regimens were safe and well tolerated. Previous COVID-19 infection was also associated with higher pre and post-booster IgG GM levels.

CONCLUSION

Although both boosting regimens were highly immunogenic, two doses of BBIBP-CorV boosted with BTN162b2 produced a stronger IgG antibody response than the homologous BNT162b2 regimen in the Peruvian population. Additionally, both regimens were mildly reactogenic and well-tolerated.

Durability of Immune Response to ChAdOx1-nCoV-19 Vaccine in Solid Cancer Patients Undergoing Anticancer Treatment

There are limited data available about the durability of the immune response after administration of the widely used adenovirus-vectored ChAdOx1-nCoV-19 vaccine in cancer patients. This prospective longitudinal observational study analyzed follow-up data of immunogenic responses 12 weeks after the second dose of the ChAdOx1-nCoV-19 vaccine in 290 oncological patients compared to healthy controls. The study aimed to assess the persistence of the humoral immune response three months after the second dose, and omicron neutralization was also evaluated. Three months after completion of the second vaccine dose, the geometric mean titer of SARS-CoV-2 binding total Ig statistically decreased by 42% compared to those at 4 weeks, and was lower than that of the healthy control. Six percent of patients became seronegative for anti-RBD total Ig. Only 5% (2 of 40 samples) tested positive for surrogate neutralization against SAR-CoV-2 Omicron BA.2. Across different therapy types, a waning in immunogenicity was observed within three months after the second dose of the ChAdOx1 nCoV-19 vaccine, rendering it insufficient at that point to protect against the SAR-CoV-2 Omicron BA.2 variant.

Immunogenicity of ChAdOx1-nCoV-19 vaccine in solid malignancy patients by treatment regimen versus healthy controls: A prospective, multicenter observational study

BACKGROUND

Limited data exists regarding the efficacy of ChAdOx1-nCoV-19 vaccine against Severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) in solid cancer patients. We aimed to assess the immunogenicity of the ChAdOx1-nCoV-19 vaccine and the impact of different anticancer therapies for solid malignancies on immune response.

METHODS

This prospective, longitudinal observational study of immunogenicity following ChAdOx1-nCoV-19 vaccination among 385 solid cancer patients on active cancer treatment was conducted in two oncology centers. Participants received the first dose between June 18 and July 27, 2021 and the second dose at 8-10 weeks later. Blood samples were evaluated for total immunoglobulins against the receptor-binding of SARS-CoV-2 spike protein (anti-RBD total-Ig) before, and 4-week after the first- and second-doses. The primary endpoint was the geometric mean titers (GMT) of antibody among solid cancer patients compared to healthy controls and the impact of different cancer treatment types.

FINDINGS

Among solid cancer patients, the antibody level increased more slowly to significantly lower levels than achieved in healthy controls. The GMT at 4-weeks post-vaccination in cancer vs. healthy were 224.5 U/ml (95%CI 176.4-285.6) vs. 877.1 U/ml (95%CI 763.5-1008), p<0.0001), respectively. For different types of cancer treatments, chemotherapy agents, especially anthracyclines (GMR 0.004; 95%CI 0.002-0.008), paclitaxel (GMR 0.268; 95%CI 0.123-0.581), oxaliplatin (GMR 0.340; 95%CI 0.165-0.484), and immunotherapy (GMR 0.203; 95%CI 0.109-0.381) showed significantly lower antibody response. Anti-HER2, endocrine therapy and 5-fluouracil or gemcitabine, however, had less impact on the immune response.

INTERPRETATION

Suboptimal and heterogeneous immunologic responses were observed in cancer patients being treated with different systemic treatments. Immunotherapy or chemotherapy significantly suppressed the antibody response.

FUNDING

Quality Improvement Fund, King Chulalongkorn Memorial Hospital, The Thai Red Cross Society and Center of Excellence in Clinical Virology at Chulalongkorn University and Chulalongkorn Medical Oncology Research Fund.

Immunogenicity after a Third COVID-19 mRNA Booster in Solid Cancer Patients Who Previously Received the Primary Heterologous CoronaVac/ChAdOx1 Vaccine

No data regarding the efficacy of a third mRNA vaccine for solid cancer patients previously primed with the heterologous CoronoVac/ChAdOx1 vaccination implemented in Thailand during the shortage of vaccine supply are available. Forty-four cancer patients who previously received the heterologous CoronaVac-ChAdOx1 regimen were boosted with a third mRNA COVID vaccine, either BNT162b2 or mRNA-1273. Anti-RBD IgG was measured immediately before, two weeks after, and four weeks after the third dose. The antibody response was compared to 87 age- and gender-matched cancer patients who were primed with the homologous ChAdOx1/ChAdOx1 regimens. Post-third dose anti-RBD IgG levels significantly increased compared to pre-third dose levels. There was no statistical difference in post-third dose antibody titers or neutralization levels between these two primary series regimens. Treatment with chemotherapy was associated with a lower antibody response compared to endocrine therapy/biologics. Similar antibody levels were observed after a third booster with either BNT162b2 or mRNA-1273 following heterologous CoronaVac/ChAdOx1 vaccination. There was no statistical difference in the immune response following the third-dose vaccination between cancer patients and healthy individuals who received the same heterologous CoronaVac/ChAdOx1 vaccination. In conclusion, a similar degree of enhanced immunogenicity was observed after a third mRNA COVID-19 vaccination in solid cancer patients who previously received the heterologous CoronaVac/ChAdOx1 regimens.

A randomized controlled trial of heterologous ChAdOx1 nCoV-19 and recombinant subunit vaccine MVC-COV1901 against COVID-19

Heterologous prime-boost COVID-19 vaccine strategy may facilitate mass COVID-19 immunization. We reported early immunogenicity and safety outcomes of heterologous immunization with a viral vector vaccine (ChAdOx1) and a spike-2P subunit vaccine (MVC-COV1901) in a participant-blinded, randomized, non-inferiority trial (NCT05054621). A total of 100 healthy adults aged 20–70 years having the first dose of ChAdOx1 were 1:1 randomly assigned to receive a booster dose either with ChAdOx1 (n = 50) or MVC-COV1901 (n = 50) at an interval of 4–6 or 8–10 weeks. At day 28 post-boosting, the neutralizing antibody geometric mean titer against wild-type SARS-CoV-2 in MVC-COV1901 recipients (236 IU/mL) was superior to that in ChAdOx1 recipients (115 IU/mL), with a GMT ratio of 2.1 (95% CI, 1.4 to 2.9). Superiority in the neutralizing antibody titer against Delta variant was also found for heterologous MVC-COV1901 immunization with a GMT ratio of 2.6 (95% CI, 1.8 to 3.8). Both spike-specific antibody-secreting B and T cell responses were substantially enhanced by the heterologous schedule. Heterologous boosting was particularly prominent at a short prime-boost interval. No serious adverse events occurred across all groups. The findings support the use of heterologous prime-boost with ChAdOx1 and protein-based subunit vaccines.

Public safety concern of the ChAdOx1 vaccine has led to an alternative immunisation strategy against SARS-CoV-2, with this heterologous schedule widely adopted and officially recommended in many countries. Here, the authors report the immunogenicity and safety outcomes of heterologous prime-boost immunisation with ChAdOx1 and a spike-2P subunit vaccine in a single-blinded, randomised trial.

Multiple sclerosis disease-modifying therapies and COVID-19 vaccines: a practical review and meta-analysis

Studies among people with multiple sclerosis (pwMS) receiving disease-modifying therapies (DMTs) have provided adequate evidence for an appraisal of COVID-19 vaccination policies among them. To synthesise the available evidence addressing the effect of MS DMTs on COVID-19 vaccines' immunogenicity and effectiveness, following the Cochrane guidelines, we systematically reviewed all observational studies available in MEDLINE, Scopus, Web of Science, MedRxiv and Google Scholar from January 2021 to January 2022 and extracted their relevant data. Immunogenicity data were then synthesised in a quantitative, and other data in a qualitative manner. Evidence from 28 studies suggests extensively lower B-cell responses in sphingosine-1-phosphate receptor modulator (S1PRM) treated and anti-CD20 (aCD20) treated, and lower T-cell responses in interferon-treated, S1PRM-treated and cladribine-treated pwMS-although most T cell evidence currently comprises of low or very low certainty. With every 10-week increase in aCD20-to-vaccine period, a 1.94-fold (95% CI 1.57 to 2.41, p<0.00001) increase in the odds of seroconversion was observed. Furthermore, the evidence points out that B-cell-depleting therapies may accelerate postvaccination humoral waning, and boosters' immunogenicity is predictable with the same factors affecting the initial vaccination cycle. Four real-world studies further indicate that the comparative incidence/severity of breakthrough COVID-19 has been higher among the pwMS treated with S1PRM and aCD20-unlike the ones treated with other DMTs. S1PRM and aCD20 therapies were the only DMTs reducing the real-world effectiveness of COVID-19 vaccination among pwMS. Hence, it could be concluded that optimisation of humoral immunogenicity and ensuring its durability are the necessities of an effective COVID-19 vaccination policy among pwMS who receive DMTs.

Real-World Effectiveness of Mix-and-Match Vaccine Regimens against SARS-CoV-2 Delta Variant in Thailand: A Nationwide Test-Negative Matched Case-Control Study

The objective of this study is to explore the real-world effectiveness of various vaccine regimens to tackle the epidemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta variant in Thailand during September–December 2021. We applied a test-negative case control study, using nationwide records of people tested for SARS-CoV-2. Each case was matched with two controls with respect to age, detection date, and specimen collection site. A conditional logistic regression was performed. Results were presented in the form vaccine effectiveness (VE) and 95% confidence interval. A total of 1,460,458 observations were analyzed. Overall, the two-dose heterologous prime-boost, ChAdOx1 + BNT162b2 and CoronaVac + BNT162b2, manifested the largest protection level (79.9% (74.0–84.5%) and 74.7% (62.8–82.8%)) and remained stable over the whole study course. The three-dose schedules (CoronaVac + CoronaVac + ChAdOx1, and CoronaVac + CoronaVac + BNT162b2) expressed very high degree of VE estimate (above 80.0% at any time interval). Concerning severe infection, almost all regimens displayed very high VE estimate. For the two-dose schedules, heterologous prime-boost regimens seemed to have slightly better protection for severe infection relative to homologous regimens. Campaigns to expedite the rollout of third-dose booster shot should be carried out. Heterologous prime-boost regimens should be considered as an option to enhance protection for the entire population.

Comparison of Immunogenicity and Safety of Inactivated, Adenovirus-Vectored, and Heterologous Adenovirus-Vectored/mRNA Vaccines in Patients with Systemic Lupus Erythematosus and Rheumatoid Arthritis: A Prospective Cohort Study

Background: Impaired immune responses to COVID-19 vaccines have been observed in autoimmune rheumatic disease patients. Determining the most effective and safe vaccine regimen is critically needed in such a population. We aim to compare the immunogenicity and safety of three COVID-19 vaccine regimens in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Methods: SLE and RA patients aged 18−65 years who received inactivated (CoronaVac or COVILO), adenovirus-vectored (AZD1222), or heterogeneous (AZD1222/BNT162b2) vaccines were enrolled. Humoral and cellular immune responses were assessed at day 28 after the second vaccination. This was performed using the serum binding antibody level against the receptor-binding domain of the SARS-CoV-2 spike protein (anti-RBD Ig) and IFNy-ELISpot assay (ELISpot), respectively. Reactogenicity was reviewed on day 7 following each vaccination. Disease activity was assessed before and on day 28 after the second vaccination. Results: The cohort consisted of 94 patients (64 SLE and 30 RA). Inactivated, AZD1222, and AZD1222/BNT162b2 vaccines were administered to 23, 43, and 28 patients, respectively. Anti-RBD titers were lowest in the inactivated vaccine group (2.84 AU/mL; 95% CI 0.96−8.44), followed by AZD1222 (233.7 AU/mL; 95% CI 99.0−505.5), and AZD1222/BNT162b2 (688.6 AU/mL; 95% CI 271−1745), p < 0.0001. After adjusting for relevant factors, the inactivated vaccine was associated with the lowest humoral response, while adenovirus-vectored/mRNA vaccine was the highest. The proportion of positive ELISpot test was also lowest in the inactivated vaccine group (27%), followed by the adenovirus-vectored vaccine (67%), and the adenovirus-vectored/mRNA vaccine (73%) (p = 0.03). All types of vaccine were well-tolerated. There was no flare of autoimmune disease post-vaccination. Conclusion: Adenovirus-vectored and adenovirus-vectored/mRNA vaccines elicited a stronger humoral and cellular immune response than inactivated vaccines, suggesting that they may be more suitable in SLE and RA patients receiving immunosuppressive therapy.

Immunogenicity of heterologous inactivated and adenoviral-vectored COVID-19 vaccine: real-world data

Limited data are available on the responses to heterologous vaccine regimens for SARS-CoV-2, especially among countries using inactivated and adenoviral-vectored vaccines. A total of 77 participants who received heterologous inactivated COVID-19 vaccine (CoronaVac) and adenoviral-vectored vaccine (AZD1222) were enrolled in our study. There were two comparison groups vaccinated with the homologous CoronaVac (N = 79) and AZD1222 (N = 78) regimen. All sera samples were tested for anti-receptor-binding-domain IgG (anti-RBD IgG) using a chemiluminescent microparticle immunoassay (CMIA). The neutralizing activity in a subset of serum samples was tested against the original Wuhan strain and variants of concern, B.1.1.7, B.1.617.2 and B.1.351, using an enzyme-linked immunosorbent assay (ELISA)-based surrogate virus neutralization test (sVNT). The heterologous CoronaVac/AZD1222 vaccine induced higher levels of anti-RBD IgG than that of two-dose homologous CoronaVac or AZD1222 vaccines (p < 0.001). Sera samples of the CoronaVac/AZD1222 vaccine recipients elicited higher neutralizing antibody activity against the original Wuhan and all variants of concern than in the recipients of the two-dose CoronaVac. The heterologous CoronaVac followed by AZD1222 is an alternative regimen to combat with the SARS-CoV-2 variants in case of vaccine shortage with improved immunogenicity compared to the homologous CoronaVac regimen.

The Pilot Study of Immunogenicity and Adverse Events of a COVID-19 Vaccine Regimen: Priming with Inactivated Whole SARS-CoV-2 Vaccine (CoronaVac) and Boosting with the Adenoviral Vector (ChAdOx1 nCoV-19) Vaccine

In response to the SARS-CoV-2 Delta variant, which partially escaped the vaccine-induced immunity provided by two doses of vaccination with CoronaVac (Sinovac), the National Vaccine Committee recommended the heterologous CoronaVac-ChAdOx1 (Oxford−AstraZeneca), a prime−boost vaccine regimen. This pilot study aimed to describe the immunogenicity and adverse events of the heterologous CoronaVac-ChAdOx1 regimen, in comparison with homologous CoronaVac, and homologous ChAdOx1. Between May and August 2021, we recruited a total of 354 participants from four vaccination groups: the CoronaVac-ChAdOx1 vaccinee (n = 155), the homologous CoronaVac vaccinee (n = 32), the homologous ChAdOx1 vaccinee (n = 47), and control group of COVID-19 patients (n = 120). Immunogenicity was evaluated by measuring the level of IgG antibodies against the receptor-binding domain (anti-SRBD) of the SARS-CoV-2 spike protein S1 subunit and the level of neutralizing antibodies (NAbs) against variants of concern (VOCs) using the plaque reduction neutralization test (PRNT) and pseudovirus neutralization test (pVNT). The safety profile was recorded by interviewing at the 1-month visit after vaccination. The anti-SRBD level after the second booster dose of the CoronaVac-ChAdOx1 group at 2 weeks was higher than 4 weeks. At 4 weeks after the second booster dose, the anti-SRBD level in the CoronaVac-ChAdOx1 group was significantly higher than either homologous CoronaVac, the homologous ChAdOx1 group, and Control group (p < 0.001). In the CoronaVac-ChAdOx1 group, the PRNT50 level against the wild-type (434.5 BAU/mL) was the highest; followed by Alpha variant (80.4), Delta variant (67.4), and Beta variant (19.8). The PVNT50 level was also found to be at its highest against the wild-type (432.1); followed by Delta variants (178.3), Alpha variants (163.9), and Beta variant (42.2), respectively. The AEs in the CoronaVac-ChAdOx1 group were well tolerated and generally unremarkable. The CoronaVac-ChAdOx1 heterologous regimen induced higher immunogenicity and a tolerable safety profile. In a situation when only CoronaVac-ChAdOx1 vaccines are available, they should be considered for use in responding to the Delta variant.