Estudo publicado na Lancet conclui que terceira dose da vacina pfiser estimula anticorpos neutralizantes contra o SARS-COV 2
DG Alerts COVID-19 Janeiro 20, 2022
Third dose of BNT162b2 vaccine elicits neutralising antibodies against SARS-CoV-2 omicron variant: Study
A third dose of BNT162b2 (Pfizer-BioNTech) vaccine elicits neutralising antibodies (NAbs) against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) omicron variant, according to a study published in The Lancet.
“Our results suggest that NAb titres (NAbTs) against omicron after a third vaccine dose of BNT162b2 are on a similar order to NAbTs against delta after a second dose of BNT162b2,” wrote Mary Wu, The Francis Crick Institute, London, UK, and colleagues.
The authors pointed out that “whereas changes in intrinsic viral characteristics such as tissue tropism or transmissibility might alter the precise level of NAbs that correlates with protection from illness, NAbTs measured in the laboratory remain the strongest correlate of protection against symptomatic and severe illness across multiple variants,” noting that “the NAbTs [observed] are broadly consistent with preliminary epidemiological data of vaccine efficacy against symptomatic disease.”
Using a high-throughput live SARS-CoV-2 neutralisation assay, the study assessed NAbTs against omicron in 620 serum samples from 364 unique participants and compared these to NAbTs against alpha and delta variants of concern (VOCs), for which there is significant vaccine efficacy data correlated with NAbTs.
In participants sampled 2–6 weeks after two-dose vaccination with BNT162b2, most (166 [83%] of 199) had a quantifiable NAbT against omicron (median 50% inhibitory concentration [IC50] 122 [interquartile range (IQR) 46–173]), which was 7-fold lower [95% confidence interval (CI) 6.3–7.4] than NAbTs against alpha (median IC50 600 [IQR 384–1,141]) and 3-fold [95% CI 2.8–3.3] lower than NAbTs against delta (median IC50 301 [IQR 171–572]). However, when sampled 12–16 weeks after two-dose vaccination with BNT162b2, only around half of participants (69 [51%] of 136) had a quantifiable NAbT against omicron, whereas nearly all still had a quantifiable NAbT against alpha (131 [96%] of 136) and delta (132 [97%] of 136) variants. The researchers found that the drop in omicron NAbT in the 10 weeks after the second dose was significant (χ2 P < 0.0001).
Meanwhile, analysis of participants who received two-dose vaccination with AZD1222 (AstraZeneca) showed that less than half of them had a quantifiable NAbT against omicron 2–6 weeks after second dose (25 [37%] of 68), dropping further (5 [19%] of 26) 12–16 weeks after second dose, whereas most participants had a quantifiable NAbT against alpha (24 [92%] of 26) and delta (21 [81%] of 26) variants at 12–16 weeks after the second dose.
Further, the researchers found that NAbTs after AZD1222 vaccination differed significantly according to whether participants reported experiencing COVID-19 symptoms (χ2 P < 0.0001). Specifically, participants who had received two doses of AZD1222 and had not experienced COVID-19 symptoms before their second vaccine dose largely had no detectable NAb response against omicron (29 [73%] of 40). In contrast, only a minority of those who had received two doses of BNT162b2 and had not experienced COVID-19 symptoms had no detectable NAb response against omicron (24 [16%] of 147), although the median NAbT against omicron in this group was significantly lower than those recipients of BNT162b2 who had experienced COVID-19 symptoms before vaccination (median IC50 92 [IQR 42–158] vs 165 [122–387]; P < 0.0001), which is consistent with previous results of NAbTs against the delta variant.
The researchers also assessed 26 participants who experienced subsequent breakthrough SARS-CoV-2 infection between April and November, 2021 after two doses of vaccine, of whom 24 were probably delta infections and presented for a study visit 1–7 weeks after a positive COVID-19 test. All participants, irrespective of vaccine type, were able to subsequently neutralise omicron (median IC50 573 [IQR 310–655]).
Additionally, the researchers analysed NAbTs among 80 participants at the time when they received a third vaccine dose (median days since second dose 192 [IQR 188–202]) and in 85 participants after receiving their third vaccine dose (median days since third dose 20 [IQR 18–22]; median age 53 years [IQR 45–59]). All participants received BNT162b2 for all three doses. Before receiving their third dose, 34 (43%) of 80 participants had detectable NAbTs against omicron, whereas nearly all participants (82 [97%] of 85) neutralised omicron after a third dose, with a median IC50 of 332 (IQR 193–596). After a third dose of BNT162b2, NAbTs against omicron at roughly 3 weeks post-vaccination were only 4-fold lower (95% CI 3.3–4.5) than against the alpha variant and only 2- fold lower (95% CI 1.7–2.0) than against the delta variant.
“These findings have two important implications. First, they suggest that available vaccines encoding the ancestral spike protein first detected in Wuhan, China, still induce a NAb response against omicron that is equivalent to that induced by infection with other recent VOCs,” the authors noted. “Second, whereas each spike variant appears to induce the highest NAbT to itself with defined hierarchy of cross-reactivity, we observe that the differential in the cross-recognition of heterologous spikes is substantially reduced after booster vaccination, in line with recent reports.”
“The results from our cohort of healthy, working-age adults support a three-dose vaccination strategy against COVID-19 for the general population, and the broad neutralising response observed suggests urgent global action to deliver three-dose vaccination might increase population immunity against current VOCs (including omicron) and help prevent the emergence of new variants,” the authors concluded.
Nonetheless, they noted that “studies from diverse populations, including older and clinically extremely vulnerable people, such as those on haemodialysis or undergoing treatment for cancer remain critical to understanding immunity in groups that are most at risk and require a larger share of health-care resources should they fall ill,” and that “it remains critical to monitor NAbTs over time in diverse cohorts.”
Reference: https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(22)00092-7/fulltext
SOURCE: The Lancet
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