Group modelling – A rambling mind

Omicron BA.2, vaccination for 5-11 year-olds, and the honeymoon period

Chart 318 for scenario UK_701 with adult vaccinations and 5-11 vacs from April 1st 2022. 17th May 1.8% ,19th July 1%, 1st Sep 2%, mean NPI relaxations and 30th Nov +2% and 10th Dec +3% additional NPIs. Omicron v4 transmission k11 = 6, BA.2 v5 k11 = 8, var_eff = 25/50/70%, fSS 7% and fmort 1.05%. Model outcomes to December 3rd 2023. Reported active cases and deaths to February 19th 2022. Serious cases for 5 variants.

I haven’t needed to make significant updates to my Coronavirus model for a while, because it has been working well.
The original Omicron variant morphed into the new BA.2 variant, and although it seems no more dangerous than its predecessor, it is thought to be between 33%-50% more transmissible. I have assumed the lower value of 33% more transmissive for this post.
I have added Omicron BA.2 as fifth variant v5 to my model, with 8 times the transmissibility of Delta, compared with the original Omicron variant v4 in the model, at 6 times the Delta transmission rate.

Pandemic modelling review

Charts 21/22/23/24 with all 4 age groups for scenario UK023 with vaccinations. 17th May 1.8% ,19th July 1% and 1st Sep 2% mean NPI relaxations. v3 transmission k11 = 1, var_eff = 70/85%, fss x1 and fmort x1. Model 800 day outcomes to April 12th 2022 to November 6th. Active, all infected and serious modelled cases

Vaccination has somewhat stabilised the SARS-Cov-2 pandemic in the UK. I summarise the capabilities that I have found necessary and useful in modelling the behaviour of the pandemic; successive variants, different population age-groups, the effect of Government NPIs, and vaccinations.

Booster jab matters

Chart 318 for scenario UK079 with vaccinations. 17th May 1.8% ,19th July 1% and 1st Sep 2% mean NPI relaxations. v3 transmission k11 = 1, var_eff = 85/95%, fss x1 and fmort x1. Model 800 day outcomes to April 12th 2022 compared with reported active cases and deaths to October 17th. Serious cases for 3 variants

Having just had my 3rd Covid jab, the “booster” jab, it provoked a few thoughts about that, my Coronavirus model, and the wider scene. I had incorporated multiple jabs into my UK model some time ago, and multiple phases for inoculation volumes to cope with the first and second jabs. I am taking this opportunity to report briefly on model outcomes for waning immunity in the context of booster jabs.

“Freedom Day”, multiple vaccinations and the Delta variant

In this post, I run a development of my model which includes immunity waning (at a 150 day half-life), vaccine hesitancy by group, multiple vaccine inoculations (representing the typical two jabs required by most vaccines for best immunity) and also the possibility of vaccinated people not only to become infected, but also to pass on the virus even if not infected themselves.

Exploring new variants, vaccines and NPIs

Chart 303 for the grouped model UK929: modelled 800 day outcome for all variants for serious cases and deaths, with 2021 NPI relaxations up to June 21st 2021

There has been increasing concern recently about SARS-Cov-2 variants that might escape vaccines to some extent, as well as having different transmission rates (as the Kent variant does), and causing different severity of illness with higher mortality. I have added a vaccination efficacy modifier, var_eff, by variant, as a multiplier to the standard vaccination efficacy, vac_eff, to help model such potential variants that have a partial or total capability to escape vaccines, and this post shows examples of how that works, using a third variant introduced to the model on January 1st 2021. In addition, I have completed adding fSS (the fraction of people becoming seriously sick from each variant) and fmort (fatality of the variant) by Covid variant.

Tuning the age and vulnerability model

Chart 19 for the grouped model UK957: modelled 800 day outcome compared with reported data to April 21st for active cases and deaths, with 2021 NPI relaxations up to June 21st 2021

In my latest post on March 26th I described a new Coronavirus group model, based on work I had done as a UK case study in support of Prof. Alex de Visscher’s paper, in conjunction with Dr. Tom Sutton, on “Second-wave Dynamics of COVID-19: Impact of Behavioral Changes, Immunity Loss, New Strains, and Vaccination” which has now been published for peer review as a pre-print on Springer’s site at https://www.researchsquare.com/article/rs-195879/v1. I have now added the latest UK vaccination progress figures, and the UK Government’s announced intentions for the near future regarding Non Pharmaceutical Interventions (NPIs). I have also updated mortality and infection characteristics for the four different population groups in the model.

Age and vulnerability related Coronavirus modelling

Chart 209 showing modelled and reported cumulative cases and deaths to 800 days in the groups model

In my most recent post on February 12th, I described modelling work I had done in support of Prof. Alex de Visscher’s paper, in conjunction with Dr. Tom Sutton, on “Second-wave Dynamics of COVID-19: Impact of Behavioral Changes, Immunity Loss, New Strains, and Vaccination” which has now been published for peer review as a pre-print on Springer’s site at https://www.researchsquare.com/article/rs-195879/v1. I have now added vaccination and multiple variants I had already added to our previous model into the new grouped population model, and this blog post reports on progress with that new model.