Can you find the key elements of this modelling study? by Y Liu

eideyliu — 2025-03-04 12:21:37 UTC

From the sound of the title, it's something about measles.

2025-03-05 02:59:10 UTC

To evaluate whether measles dynamics observed in England between 2010 and 2019 were in line with a waning of vaccine-induced immunity.

2025-03-05 03:00:28 UTC

vaccination data from COVER and CPRD, first and second dose coverage from UKHSA

2025-03-05 03:04:03 UTC

scenario analysis: without the waning of immunity, waning of immunity increasing with each year of age from 5 years, the waning of immunity increasing with each year of age from 5 years and from the year 2000

wly213 — 2025-03-05 03:05:35 UTC

the authors want to evaluate whether measles dynamics observed in England

between 2010 and 2019 were in line with a waning of vaccine-induced immunity.

2025-03-05 03:06:31 UTC

Which of the three scenarios is the measles transmission dynamics most consistent with?

2025-03-05 03:07:35 UTC

Unknown vaccination status was set as unvaccinated

2025-03-05 03:07:43 UTC

vaccination status of some individual (n=143) were classified as one-dose recipients on the basis that a) no other individuals were classified as one-dose between 2014-2019 (whereas n=152 classified as two-doses) and 19/143 were 3 years old and younger, younger than the recommended age for the 2nd dose of vaccine

2025-03-05 03:09:29 UTC

SEIR model would represent the transmission dynamics of measles well

2025-03-05 03:09:34 UTC

Vaccine efficacy wanes at the same rate for one-dose and two-dose recipients

wly213 — 2025-03-05 03:09:45 UTC

the number of daily cases per age group, region, and vaccine status in England between 2010 and 2019.

2025-03-05 03:10:10 UTC

risk of infection being the same for all individuals in a given age group

2025-03-05 03:10:56 UTC

Input parameters:

Duration of latent and infectious period
Timing and duration of outbreak
Seasonality of importations
Number of importations by region

2025-03-05 03:11:34 UTC

In waning scenarios, waning starts at age of 5

2025-03-05 03:11:57 UTC

All double-vaccinated individuals are vaccinated by 5 years old, hence late-vaccinees were not considered, and immunity wanes at the same rate in all vaccinated individuals.

2025-03-05 03:12:09 UTC

Waning of vaccine-induced immunity assumed to be linear

2025-03-05 03:12:32 UTC

Measles case dynamics in England were consistent with scenarios assuming the waning of vaccine-induced immunity. While most transmissions were connected to people who are unvaccinated, breakthrough infections are increasingly frequent for individuals who have been vaccinated twice. While the vaccine remains highly protective against measles infections, slow waning leads to a heightened burden in outbreaks, increasing the number of measles cases in people who are both vaccinated and unvaccinated

2025-03-05 03:13:17 UTC

Waning of vaccine-induced immunity follows a step-wise function (in predefined basket of ages)

2025-03-05 03:13:38 UTC

to generate stochastic simulations where transitions between compartments were treated as a stochastic process. The stochastic simulations showed the set of dynamics the parameter estimates could generate, with a higher variance than the deterministic fits. Fitting a stochastic version of the model was not computationally feasible given the number of compartments and stratum.

2025-03-05 03:15:45 UTC

in ref analysis, it assumes that only infection-induced immunity for individuals born before and in 1970s

2025-03-05 03:15:54 UTC

sensitivity analyses: to assess whether the effect of waning of immunity was robust to changes in assumptions, including:

(1) the addition of a constant risk of secondary vaccine failure but is not waning over time

(2) using the COVER data without adjustment for under-ascertainment, and using the CPRD data to compute the proportion of newly vaccinated individuals at the age of 3 years and 4 years

(3) estimating the proportion of individuals aged 30–39 years in 2010 who received one dose of the vaccine

(4) fixing the cross-regional transmission rate to test different transmission patterns between regions

(5) setting the start of waning to 1995 in a scenario where waning depends on both age and time since end of endemicity

2025-03-05 03:17:13 UTC

Contact pattern between age groups is quantified by a contact matrix, computed from the POLYMOD study

2025-03-05 03:19:54 UTC

Migration of inhabitants is not considered in the model. Instead, a spatial kernel was included to quantify the rate of transmission from one region to another

2025-03-05 03:20:08 UTC

Reference analysis assumed that only infection-induced immunity (ie, providing full non-waning protection) was possible in the 30-39 year age group due to difficulties estimating the vaccination status for these individauls due to routine vaccination only starting in 1968, and the presence of catch-up vaccination campaigns

2025-03-05 03:20:21 UTC

In all modelled scenarios, the R0 was estimated between 16 and 18 (scenarios without waning: 16·6 [95% credible interval (CrI): 16·2–17·0]; scenarios with waning: 17·2 [16·9–17·6]; scenarios with waning starting in 2000: 17·1 [16·8–17·4]; figure 5A; appendix p 18), which is within the typical range for measles (between 12 and 18).

wly213 — 2025-03-05 03:20:23 UTC

three scenarios: (1): without the waning of immunity (ie, transmission between the vaccinated and the exposed compartments is only possible in the case of primary vaccine failure) (2): with the waning of immunity increasing with each year of age from 5 years, and with the waning of immunity increasing with each year of age from 5 years and from the year 2000. (3): individuals vaccinated before 2000 had full protection until 2000, when the waning of immunity is then linked to the low rates of transmission observed since 2000 in England.

2025-03-05 03:22:22 UTC

Thorough documentation of the entire process is key to allowing readers to understand, interpret and critique the chosen approach

2025-03-05 03:22:52 UTC

The proportion of measles cases that are two-dose recipients is increasing faster in the data than in all simulated scenarios, so waning dynamics might be more complex than what we tested.

2025-03-05 03:23:19 UTC

Lots of data from multiple sources are required for ID modelling

2025-03-05 03:28:32 UTC

Input data - vaccination data from

COVER
CPRD

2025-03-05 03:37:15 UTC

did increased measles cases observed in England between 2010 and 2019 were due to a waning of vaccine-induced immunity?

2025-03-05 03:41:15 UTC

7504 confirmed measles cases in England between 2010 and 2019 collected by Public Health England including the date of symptom onset, region of residence,

age, and vaccine status of each individual

2025-03-12 12:40:17 UTC

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