Covid-19, pneumococcal and flu vaccines: a Chinese trial evaluates coadministration

Two appointments, three vaccines studied

This phase IV, randomized, multicenter, open-label trial included equal numbers of adults aged 18 to 59 and people aged 60 or over. It evaluated three specific products: the inactivated SARS-CoV-2 vaccine WIBP-CorV, the 23-valent pneumococcal polysaccharide vaccine PPV23 and an inactivated quadrivalent influenza vaccine, IIV4.

Participants were assigned to three groups. The first received WIBP-CorV with PPV23 on day 0, then WIBP-CorV with IIV4 on day 28. The second received only WIBP-CorV on both dates. The third received PPV23 on day 0, then IIV4 on day 28. The trial therefore did not involve administering all three vaccines on the same day.

Favorable results, but not across all criteria

According to the abstract, non-inferiority was demonstrated for the geometric mean titers of SARS-CoV-2-neutralizing antibodies and geometric mean concentrations of IgG against pneumococcal serotypes. This approach seeks to establish that the response does not decrease beyond a predefined margin, whose value is not provided in the excerpt.

Seroconversion rates also met the non-inferiority criteria for all pneumococcal serotypes studied. Results were less consistent for SARS-CoV-2 after the second dose and for the A(H1N1) influenza strain. Analyses by age and strain also call for caution.

Reassuring tolerability within the trial’s limits

The authors report slightly more frequent mild, transient local reactions with coadministration, with no serious adverse events attributed to the vaccines. However, the abstract provides neither the absolute frequencies of these reactions nor the full duration of follow-up. These observations do not rule out rare adverse effects.

What this changes, and what it does not show

The trial supports the immunological feasibility of these specific combinations in the adults represented. It does not demonstrate an equivalent reduction in infections, hospitalizations or deaths: the results presented concern antibodies, not these clinical outcomes.

These conclusions cannot automatically be generalized to other Covid-19 vaccines or other formulations. Nor do they constitute a vaccination recommendation applicable in France.

What we can take away

The coadministration regimen studied preserves several antibody responses, but results vary by criterion and strain. Preserving immunogenicity is not enough to demonstrate equivalent clinical protection.