3. Safety, Immunogenicity and Efficacy of COVID-19 and Influenza Vaccine Co-Administration
As of February 2022, three randomized controlled trials (RCTs)
[30][31][32] on COVID-19 and SIV vaccine co-administration are available. In a phase IV trial conducted in the United Kingdom (UK)
[30], adults were randomized (1:1;
n = 679) to receive either a second dose of ChAdOx1 (Vaxzevria, AstraZeneca, Cambridge, UK) or BNT162b2 vaccines, together with an age-appropriate SIV (QIVc, recombinant quadrivalent influenza vaccine (QIVr; Supemtek, Sanofi Pasteur, Lyon, France) for subjects aged 18–64 years and MF59-adjuvanted trivalent influenza vaccine (aTIV; Fluad, Seqirus) for those aged ≥65 years) or ChAdOx1/BNT162b2 together with placebo. Three weeks later, those who had received placebo received SIV, and vice versa. Toback et al.
[31] reported the results of a phase III efficacy RCT, in which a subset of adults was randomized (1:1;
n = 431) to receive the first dose of NVX-CoV2373 (Nuvaxovid, Novavax CZ a.s., Jevany, Czech Republic) plus SIV (QIVc and aTIV for subjects aged 18–64 and ≥65 years, respectively) or SIV alone. Finally, the interim results of a phase II RCT have recently been reported
[32]; in this trial, elderly individuals (≥65 years) were randomized (1:1:1;
n = 431) to receive a second dose of mRNA-1273 (Spikevax, Moderna, Cambridge, MA, USA) plus a high-dose quadrivalent influenza vaccine (hdQIV; Fluzone High-Dose Quadrivalent, Sanofi Pasteur, Lyon, France), a dose of hdQIV alone or a second dose of mRNA-1273 alone. In all three RCTs
[31][32], vaccines were co-administered in opposite arms in each subject.
All three RCTs
[31][32] reported no major safety concerns regarding COVID-19 + SIV co-administration. Specifically, as reported in
Table 1, the overall rate of solicited local (especially pain in the injection site) and systemic adverse events was similar between subjects who received COVID-19 + SIV and those who received the COVID-19 vaccine alone. The adverse events reported were mostly mild-to-moderate and self-limiting. A similar picture was seen with regard to unsolicited adverse events.
Table 1. Rate (%) of solicited local and systemic adverse events in COVID-19 and influenza vaccine co-administration groups, as compared with groups to whom either vaccine was administered alone.
Adverse Event |
Comparison |
Vaccine Administration Pattern |
Reference |
COVID-19 Vaccine |
SIV |
COVID-19 + SIV |
COVID-19 Alone |
SIV Alone |
Any local, % |
ChAdOx1 1 |
QIVc 1 |
84 |
81 |
– |
[30] |
BNT162b2 1 |
QIVc 1 |
96 |
94 |
– |
[30] |
ChAdOx1 1 |
QIVr 1 |
85 |
86 |
– |
[30] |
BNT162b2 1 |
QIVr 1 |
96 |
89 |
– |
[30] |
ChAdOx1 2 |
aTIV 2 |
77 |
65 |
– |
[30] |
BNT162b2 2 |
aTIV 2 |
76 |
79 |
– |
[30] |
mRNA-1273 2 |
hdQIV 2 |
86 |
91 |
62 |
[32] |
NVX-CoV2373 1 |
QIVc 1 |
73 |
63 |
39 |
[31] |
NVX-CoV2373 2 |
aTIV 2 |
39 |
35 |
46 |
[31] |
Any systemic, % |
ChAdOx1 1 |
QIVc 1 |
81 |
83 |
– |
[30] |
BNT162b2 1 |
QIVc 1 |
87 |
81 |
– |
[30] |
ChAdOx1 1 |
QIVr 1 |
74 |
72 |
– |
[30] |
BNT162b2 1 |
QIVr 1 |
89 |
82 |
– |
[30] |
ChAdOx1 2 |
aTIV 2 |
72 |
62 |
– |
[30] |
BNT162b2 2 |
aTIV 2 |
59 |
71 |
– |
[30] |
mRNA-1273 2 |
hdQIV 2 |
80 |
84 |
49 |
[32] |
NVX-CoV2373 1 |
QIVc 1 |
62 |
50 |
47 |
[31] |
NVX-CoV2373 2 |
aTIV 2 |
39 |
28 |
55 |
[31] |
1 Working-age adults (18–64 years); 2 older adults (≥65 years); aTIV, MF59-adjuvanted trivalent influenza vaccine; hdQIV, high-dose quadrivalent influenza vaccine; QIVc, cell-based quadrivalent influenza vaccine; QIVr, recombinant quadrivalent influenza vaccine.
It has generally been found
[30][31][32] that the humoral IgG response measured by means of the hemagglutination inhibition (HAI) assay approximately 3 weeks after immunization towards any SIV strain is preserved in COVID-19 + SIV co-administration groups. Indeed, apart from the statistical significance, geometric mean ratios of all pairwise comparisons have proved to be >0.67, which is the non-inferiority margin (
Table 2). Lazarus et al.
[30] did not observe any significant difference in geometric mean titers (GMTs) between most co-administration groups (ChAdOx1 + QIVc, ChAdOx1 + QIVr, ChAdOx1 + aTIV, BNT162b2 + QIVc or BNT162b2 + aTIV) and groups receiving SIVs alone. The only exception was the immune response to A(H1N1)pdm09, B/Victoria and B/Yamagata; in these cases, GMTs were 20–38% higher in the BNT162b2 + QIVr group than in individuals who received QIVr only. The IgG response to A(H3N2) was similar. Toback et al.
[31] did not find any significant difference in HAI titers between COVID-19 + SIV and placebo + SIV groups, regardless of the strain or vaccine (QIVc or aTIV). Analogously, the humoral immune response towards all four SIV strains was similar in individuals who received mRNA-1273 + hdQIV or hdQIV alone
[32].
Table 2. Hemagglutination inhibition IgG geometric mean ratios against influenza vaccine strains in COVID-19 + seasonal influenza vaccine co-administration groups, as compared with groups to whom either vaccine was administered alone.
Influenza Vaccine |
Strain |
COVID-19 Vaccine [Reference] |
BNT162b2 [30] |
mRNA-1273 [32] |
ChAdOx1 [30] |
NVX-CoV2373 [31] |
QIVc 1 |
A(H1N1)pdm09 |
1.05 (0.91–1.21) 4 |
– |
1.05 (0.91–1.21) 4 |
1.09 (ns) 6 |
A(H3N2) |
1.06 (0.95–1.18) 4 |
– |
1.08 (0.96–1.21) 4 |
1.08 (ns) 6 |
B/Victoria |
1.03 (0.93–1.14) 4 |
– |
1.05 (0.94–1.18) 4 |
1.03 (ns) 6 |
B/Yamagata |
0.94 (0.85–1.05) 4 |
– |
0.98 (0.88–1.10) 4 |
0.99 (ns) 6 |
QIVr 1 |
A(H1N1)pdm09 |
1.38 (1.11–1.71) 4 |
– |
0.86 (0.74–0.99) 4 |
– |
A(H3N2) |
1.03 (0.87–1.23) 4 |
– |
1.03 (0.91–1.15) 4 |
– |
B/Victoria |
1.20 (1.02–1.42) 4 |
– |
1.07 (0.96–1.19) 4 |
– |
B/Yamagata |
1.24 (1.05–1.47) 4 |
– |
1.06 (0.94–1.18) 4 |
– |
aTIV 2 |
A(H1N1)pdm09 |
1.05 (0.87–1.27) 4 |
– |
1.15 (1.01–1.32) 4 |
1.41 (ns) 6 |
A(H3N2) |
1.18 (1.02–1.37) 4 |
– |
1.00 (0.89–1.11) 4 |
0.87 (ns) 6 |
B/Victoria |
1.08 (0.94–1.25) 4 |
– |
1.01 (0.91–1.12) 4 |
0.54 (ns) 6 |
B/Yamagata 3 |
1.00 (0.86–1.15) 4 |
– |
0.92 (0.83–1.03) 4 |
0.81 (ns) 6 |
hdQIV 2 |
A(H1N1)pdm09 |
– |
0.99 (ns) 5 |
– |
– |
A(H3N2) |
– |
0.91 (ns) 5 |
– |
– |
B/Victoria |
– |
0.97 (ns) 5 |
– |
– |
B/Yamagata |
– |
0.91 (ns) 5 |
– |
– |
1 Working-age adults (18–64 years); 2 older adults (≥65 years); 3 strain was not present in the vaccine formulation; 4 seasonal influenza vaccine first vs. placebo first; 5 mRNA-1273 + hdQIV vs. hdQIV alone, geometric mean ratios were calculated from the geometric mean titers provided by the authors; 6 NVX-CoV2373 + seasonal influenza vaccine vs. placebo + seasonal influenza vaccine, geometric mean ratios were calculated from the geometric mean titers provided by the authors; aTIV, MF59-adjuvanted trivalent influenza vaccine; hdQIV, high-dose quadrivalent influenza vaccine; ns, non-significant (p > 0.05); QIVc, cell-based quadrivalent influenza vaccine; QIVr, recombinant quadrivalent influenza vaccine.
Similar results were reported with regard to anti-spike neutralizing antibody titers (
Table 3). Lazarus et al.
[30] and Izikson et al.
[32] did not find any significant differences between the co-administration groups and individuals who received COVID-19 vaccines alone. By contrast, some immunological inference was reported in the RCT by Toback et al.
[31] After adjustment for baseline titers, age and the treatment arm, the geometric mean ratio of the anti-spike humoral response in NVX-CoV2373 + QIVc/aTIV versus NVX-CoV2373 alone was 0.57 (95% CI: 0.47–0.70). On the other hand, this decrease did not seem to translate into a corresponding decrease in vaccine efficacy. For instance, absolute vaccine efficacy against laboratory-confirmed symptomatic COVID-19 in adults (18–64 years) was 87.5% (95% CI: −0.2–98.4%) and 89.8% (95% CI: 79.7–95.5%) in the influenza sub-study and main study, respectively
[31].
Table 3. Anti-spike IgG geometric mean ratios in COVID-19/influenza vaccine co-administration groups, as compared with groups to whom either vaccine was administered alone.
Influenza Vaccine |
COVID-19 Vaccine [Reference] |
BNT162b2 [30] |
mRNA-1273 [32] |
ChAdOx1 [30] |
NVX-CoV2373 [31] |
QIVc 1 |
0.90 (0.80–1.01) 3 |
– |
0.92 (0.81–1.04) 3 |
0.66 (NA) 5 |
QIVr 1 |
0.86 (0.72–1.03) 3 |
– |
0.92 (0.81–1.04) 3 |
– |
aTIV 2 |
0.97 (0.83–1.13) 3 |
– |
1.02 (0.91–1.14) 3 |
0.71 (NA) 5 |
hdQIV 2 |
– |
0.97 (0.79–1.19) 4 |
– |
– |
1 Working-age adults (18–64 years); 2 older adults (≥65 years); 3 COVID-19 vaccine + placebo vs. COVID-19 vaccine + seasonal influenza vaccine; 4 mRNA-1273 + hdQIV vs. hdQIV alone; 5 NVX-CoV2373 + seasonal influenza vaccine vs. placebo + NVX-CoV2373 alone, geometric mean ratios were calculated from the geometric mean titers provided by the authors; aTIV, MF59-adjuvanted trivalent influenza vaccine; hdQIV, high-dose quadrivalent influenza vaccine; NA, not available; QIVc, cell-based quadrivalent influenza vaccine; QIVr, recombinant quadrivalent influenza vaccine.