Potential impact of Covid-19 response measures on invasive pneumococcal disease in England and Wales

Choi, Y. H.; Miller, E.

In January 2020, the United Kingdom (UK) removed one of the two infant doses of the 13-valent pneumococcal conjugate vaccine (PCV13), leaving a single priming dose at 3 months and a 12 month booster. We modelled the potential impact on invasive pneumococcal disease (IPD) of a drop in PCV13 coverage associated with the restrictions on non-essential health care visits introduced to combat COVID-19 in the UK on 23 March 2020. Using a previously published model of pneumococcal transmission in England and Wales we simulated the impact of reducing PCV13 coverage by 50% for 3 months from 23 March without subsequent catch-up vaccination. To implement social distancing, we reduced mixing between and within age-groups by either 10% or 50%. In a sensitivity analysis we explored the effect of complete cessation of PCV13 vaccination during the lockdown and of extending its duration to 6 months. Annual numbers of IPD cases predicted by the model under different vaccination and lockdown scenarios with uncertainty intervals (UI) generated from the minimum and maximum values of the model predictions using 500 parameter sets with values within a pre-specified range of the maximum likelihood set. The model predicted that any increase in IPD cases from a reduction in PCV13 coverage would be more than offset by a reduction in pneumococcal transmission due to social distancing, with a net reduction in cumulative IPD cases (UI -1,479, -1,061, all ages) over the next five years. Similar results were obtained in the sensitivity analysis, though with a greater reduction with a 6 month lockdown. COVID-19 social distancing measures are predicted to have had a profound effect on pneumococcal transmission resulting in a reduction in pneumococcal carriage prevalence and IPD incidence over the first two years after the lockdown. Carriage studies will be informative in confirming the predicted impact of the social distancing measures after they have been lifted.