key: cord-0430425-qxdvrj7q authors: Mok, C. K. P.; Hui, D. S. title: Comparison of the immunogenicity of BNT162b2 and CoronaVac COVID-19 Vaccines in Hong Kong date: 2021-10-30 journal: nan DOI: 10.1101/2021.10.28.21265635 sha: db821245fa12e1164031c2f2dced10fd9a691dd4 doc_id: 430425 cord_uid: qxdvrj7q Background. Few head-to-head evaluations of immune responses to difference vaccines have been reported. Methods. Surrogate virus neutralization test (sVNT) antibody levels of adults receiving either 2 doses of BNT162b2 (n=366) or CoronaVac (n=360) vaccines in Hong Kong were determined. An age-matched subgroup (BNT162b2 (n=49) vs CoronaVac (n=49)) were tested for plaque reduction neutralizing (PRNT) and spike binding antibody and T cell reactivity in peripheral blood mononuclear cells (PBMC). Findings. One month after the second dose of vaccine, BNT162b2 elicited significantly higher PRNT50, PRNT90, sVNT, spike receptor binding, spike N terminal domain binding, spike S2 domain binding, spike FcR binding and antibody avidity levels than CoronaVac. The geometric mean PRNT50 titres in those vaccinated with BNT162b2 and CoronaVac vaccines were 251.6 and 69.45 while PRNT90 titres were 98.91 and 16.57, respectively. All of those vaccinated with BNT162b2 and 45 (91.8%) of 49 vaccinated with CoronaVac achieved the 50% protection threshold for PRNT90. Allowing for an expected seven-fold waning of antibody titres over six months for those receiving CoronaVac, only 16.3% would meet the 50% protection threshold versus 79.6% of BNT162b2 vaccinees. Age was negatively correlated with PRNT90 antibody titres. Both vaccines induced SARS-CoV-2 specific CD4+ and CD8+ T cell responses at 1-month post-vaccination but CoronaVac elicited significantly higher structural protein-specific CD4+ and CD8+ T cell responses. Conclusion. Vaccination with BNT162b2 induces stronger humoral responses than CoronaVac. CoronaVac induce higher CD4+ and CD8+ T cell responses to the structural protein than BNT162b2. and in experimental animal models (6) . T cell immune responses are consistently elicited after natural infection and correlate with reduced disease severity in humans and reduced viral loads in non-human primates (7) (8) (9) (10) (11) . The safety, immunogenicity and efficacy of these vaccines have been evaluated in separate clinical trials (12-14) but there are few "head-to-head" comparisons of different vaccines. Here, we compare the humoral and cellular responses from vaccinees who received either BNT162b2 or CoronaVac. Role of the funding source. The sponsor of the study had no role in study design, data collection, data analysis, data interpretation, or writing of the report. The corresponding authors had full access to all the data in the study and had final responsibility for the decision to submit for publication. Adult volunteers (age range 18-79 years) were recruited between March 10 and August 31, 2021; 366 of whom received two doses of BNT162b2 and 360 received two doses of CoronaVac. The mean (SD) age of the two groups were 45.01 (13.16) and 51.78 (9.92) years respectively (p<0.0001). Demographic information is summarized in Supplementary Table 1 . We used sVNT, which has high overall concordance to the PRNT (15,16), to examine the level of SARS-CoV-2 specific neutralizing antibody from the plasma samples collected before and at 1 month after the 2nd dose of vaccination. The plasma samples from all vaccinees before vaccination were negative in sVNT (data not shown). The mean % inhibition in the sVNT test in post-vaccine plasma for BNT1626 and CoronaVac was 93.63% (standard deviation (SD) 7.92) and 52.11% (SD 22.06), respectively (p<0.0001) ( Figure 1A ). From the data above, we estimated that a sample size of 49 for each vaccine group provided statistical power higher than 80% with 95% confidence level to discern differences between the two vaccines. To avoid age-related bias, we randomly 49 selected age-matched samples from BNT162b2 or CoronaVac vaccinees for more detailed analysis. The demographic, underlying co-morbidities and other potential risk-factors were shown in Table 1 . The mean % inhibition in the sVNT test in post-vaccine plasma for BNT1626 and CoronaVac was 94.8% (standard deviation (SD) 3.45) and 63.9% (SD 16.72), respectively (p=7.71x10 -17 ) ( Figure 1B) . PRNT is the gold-standard method to evaluate virus neutralization. All vaccinees developed detectable PRNT 50 antibody titers. BNT162b2 vaccinees had significantly higher geometric mean titers (GMT) of 251.60 (±1SD range from 147 to 432) compared to 69.45 (±1SD range from 28 to 172) for the CoronaVac group (p=1.24x10 -9 ) ( Figure 1C ). The corresponding PRNT 90 antibody responses for BNT162b2 (GMT 98.91, ±1SD range from 44 to 221) was significantly higher than for CoronaVac vaccines (GMT 16.57, ±1SD range from 5 to 54) (p=5.82x10 -10 ) ( Figure 1D ). It has been suggested that the neutralizing antibody titer associated with protection from re-infection in 50% of individuals is 20% of the mean convalescent antibody levels (5). Using RT-PCR confirmed convalescent symptomatic patients sera (16), using the same PRNT methods, we estimated that this 20% convalescent antibody titer threshold for 50% protection from re-infection for PRNT 90 was 1:8.75 (95% CI 1:6.6-1:11.6) (Supplementary Figure 1) Table 3 ). Antibodies against different domains of the spike can facilitate protection (18, 19, 20) . Thus, we further tested the levels of IgG antibodies specifically binding to the RBD, NTD and S2 domains of the spike protein, respectively. While both vaccines elicited significant increases in these antibodies as detected by ELISA, BNT162b2 vaccine elicited significantly higher antibody levels to all three antigens ( Figure 1E Furthermore, increased ADCC function is associated with mRNA (22) and protein (23) vaccination and reduced morbidity during infection (24, 25) , and is therefore regarded as one of the indicators of immune protection. We found that recipients from both BNT162b2 or CoronaVac elicit increases of FcγRIIIa binding spike antibodies after two doses of vaccination ( Figure 2A ). However, the antibody level from the BNT162b2 group was significantly higher than the CoronaVac group. CoronaVac recipients had higher levels of FcγRIIIa binding antibodies to N than the BNT162b2 group after vaccination (p <0.0001) as expected, but CoronaVac N-FcγRIIIa responses were still significantly lower than COVID-19 cases ( Figure 2B ). FcγRIIIa binding is more likely to result in downstream signaling leading to effector function if antibodies have high avidity (26). S-specific FcγRIIIa as well as S-IgG avidity was significantly lower in CoronaVac recipients than BNT162b2 recipients or COVID-19 convalescent patients ( Figure 2C , D). The average avidity of N specific FcγRIIIa from CoronaVac recipients were comparable to the patients with COVID-19 ( Figure 2E ). Figure 3A and B). The magnitude of the post vaccination CD4 + T cell response after stimulation of S only peptides was also significantly higher in CoronaVac group but their CD8 + T cell responses was comparable to the BNT162b2 group (Supplementary Figure 4 A and B) . Overall, the proportion of subjects that had detectable post vaccination T cell responses (% of IFNγ + cell is higher than 0.001), termed 'responders' was higher in CoronaVac recipients than BNT162b2 recipients, for either SNEM peptides or S peptides alone ( Table 2) . Figure 4D ). Using a cohort of RT-PCR confirmed convalescent sera from COVID-19 patients, using the assays we have used in the present study, we estimated the 20% convalescent antibody titer threshold for 50% protection from re-infection for PRNT 90 was 1:8.75 (95% CI 1:6.6-1:11.6) (5,16). We conclude that all those vaccinated with BNT162b2 and 91.8% of those vaccinated CoronaVac achieved the 50% protection threshold one month after the second dose of vaccination. One month post-second dose likely represents the peak antibody response, beyond which antibody titers are likely to wane. It was reported that neutralizing antibody titres wane All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 30, 2021. ; https://doi.org/10.1101/2021.10.28.21265635 doi: medRxiv preprint 7.3-fold within 6 months after CoronaVac vaccination (17) but comparable data is not available from BNT126b2. If we adjust for a 7.3-fold waning of antibody titres for both vaccines, we estimate that only 8 (16.3%) of 49 receiving CoronaVac vaccines meet the protective threshold while 39 (79.6%) of 49 of those receiving BNT162b2 do so, 6 months post-vaccination. This difference in immunogenicity may explain reported difference in vaccine efficacy between the two vaccines (27-30). Many Phase 3 studies assessed protection within 1 to 3 months after the second dose of vaccine and may not reflect the impact of waning immunity. Furthermore, some of the virus variants (e.g. B.1.351 Beta variant; P1 Gamma variant) circulating in parts of the world lead to an 8 to 10-fold reduction in neutralizing titers and this is likely to further compromise protection afforded by CoronaVac vaccines with its weaker immunogenicity. Our results suggest that booster doses may be required for older CoronaVac recipients and such booster doses. A third dose of CoronaVac vaccine appears to boost antibody levels (17) and our data suggest that these may be needed for older CoronaVac recipients. The average magnitude of post vaccination responses was higher in CoronaVac subjects for structural and S-specific T cell responses. Since it is likely that T cell responses are important in limiting severity and fatal outcomes (7-11), both vaccines may be effective in preventing such adverse outcomes of COVID-19. This is consistent with high levels of protection against hospitalization and death in CoronaVac vaccines observed in Chile and Turkey despite lower antibody neutralization titers than BNT162b2 (30, 31). In animal models of re-infection, spike-specific CD8 + T cell responses can compensate for inadequate antibody responses (24) and are also highly cross-reactive to different variants of concern (32). Therefore, SARS-CoV-2 specific T cells may provide an additional contribution to the immune correlate of protection. An advantage of inactivated vaccines is that they also contain additional viral antigens, such as the highly abundant and immunogenic N protein which may also elicit T-cell immunity (33) and contributed to the higher responses in CoronaVac subjects here. Sampling at earlier timepoints (day 7-14) post vaccination may reveal differences in response magnitude given the phenotypic expansion of S-specific TEM CD4 + T cells by the BNT162b2 vaccine which may also have greater recall potential at infection (34) . Longitudinal follow-up is thus necessary to confirm the long-term T cell responses between the two vaccines. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 30, 2021. ; Proline mutations used in BNT162b2 vaccine to stabilize the spike protein in its pre-fusion state (35) and the serial passages in Vero cells and inactivation procedures used in the CoronaVac vaccine (36) are differences that may contribute to the differences in neutralizing antibody responses elicited by the two vaccines. Preliminary results from another study has recently reported a marked difference of immunogenicity between BNT162b2 and CoronaVac in healthcare workers (37) . However, the median age of the two groups were 37 and 47 years old respectively in that study while our subgroup was designed to be age matched. Moreover, the ADCC and T cell responses were not examined in their cohort. There were some limitations in our study. The choice of vaccine was not randomized and there might be a selection bias in those opting for each vaccine. Our study only focused on investigating the immunogenicity at 1 month after two doses of vaccination. The durability of immune responses needs to be monitored; and indeed, this cohort will be followed up to address this question in the coming years. Our estimates to adjust for antibody waning was based on reports on CoronaVac, comparable to data for BioNTech was lacking. Thus our assumption of comparable rates of antibody waning for the two vaccines may not be correct. We did not collect plasma prior to the second dose of vaccine to assess the effect of the first dose of the vaccine, or acute phase responses, where earlier responses may account for the final post vaccine differences as our primary study endpoint was neuralization titers after vaccination. Similar comparisons between vaccines in teenagers and older adults will be needed. Our data showed that the levels of antibodies elicited by CoronaVac were significantly lower than those of BNT162b2 in PRNT 50 , PRNT 90 , sVNT, spike RBD ELISA, spike NTD ELISA and spike S2 ELISA assays, and total and high avidity FcgRIIIa spike. CoronaVac induce higher CD4 + and CD8 + T cell responses to the structural protein than BNT162b2. 1) Huang C, Wang Y, Li X, Ren L, Zhao J, Hu Y, Zhang L, Fan G, Xu J, Gu X, Cheng Z, Yu T, All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 30, 2021. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 30, 2021. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 30, 2021. ; (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 30, 2021. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted October 30, 2021. ; (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. C All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. 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