org355: Groundbreaking RSV study

From The Guardian. This is a rare, welcome example of an article which presents the raw figures underlying the RR (the epidemiologic measure of effect). And so we can get start to consider the public health impact.

1. What is the PICO for this study?

2. Calculate the relative risk (RR).

A vaccine could reduce by 80% the numbers of babies and young children admitted to hospital with respiratory syncytial virus (RSV), a “groundbreaking” study has found.

3. How does the RR you calculated in #2 connect to the statement above?

4. Explain whether this RR is an efficacy or effectiveness figure.

5. Was it ethical to randomly allocate babies to a placebo?

The research found that, of the babies who received the vaccine, only 11 (0.3%) were hospitalised, in comparison with the 60 babies (1.5%) who were hospitalised after receiving just the standard care.

6. Are these incidence or prevalence figures?

7. Calculate and interpret a number needed to treat (more specifically, the number needed to vaccinate)?

In England, RSV is a leading cause of infant hospitalisation, with nearly 31,000 children aged four and under admitted each year with conditions linked to the virus. RSV causes between 20 and 30 infant deaths a year in the UK,

8. With 100% RSV vaccine uptake, what is the impact on these figures? (slight trick question, but I'm curious to read what you say!)

Re: Groundbreaking RSV study

by | MADHUTANDRA SARKAR - Wednesday, 14 February 2024, 4:33 PM

Hi Sujit,

The following are my answers:

1. The PICOs are: 
P (Population of interest): Healthy babies aged up to 12 months.
I (Intervention or exposure): Monoclonal antibody nirsevimab.
C (Comparison): Babies receiving standard care.
Outcome: Hospital admissions.
S (Study design): Randomised controlled trial.
S (Setting): UK, France, Germany.

2. Relative risk = Incidence risk of hospital admissions with RSV in infants who received nirsevimab ÷ Incidence risk of hospital admissions with RSV in infants who received standard care = (11/4037 x 100) ÷ (60/4021 x 100) = 0.27 ÷ 1.49 = 0.18.

3. My calculated RR is 0.18. So, nirsevimab will reduce the risk of hospital admissions with RSV by 82%.

4. This RR is an efficacy figure as the effect of nirsevimab is determined here under trial condition.

5. It was not ethical to randomly allocate babies to a placebo as a standard treatment for this condition is already in routine use.

6. These are incidence figures.

7. Number needed to vaccinate = 1 / (Incidence risk in infants who received standard care – Incidence risk in infants who received nirsevimab) = 1 / (1.49 – 0.27) = 1 / 1.22 = 0.8196.

On an average, 82 infants must be vaccinated with nirsevimab to prevent one case of hospital admission with RSV.

8. Here, RSV vaccine uptake is 100%.

Vaccine efficacy = (Incidence risk in infants who received standard care – Incidence risk in infants who received nirsevimab) / Incidence risk in infants who received standard care
= (1.49 - 0.27) / 1.49
= 1.22 / 1.49
= 82%

Among those who will receive nirsevimab, 82% cases of hospital admissions with RSV can be prevented.

So, each year (31000 x 82/100) = 25420 hospital admissions with RSV among children aged four and under can be prevented.

Looking forward to your feedback!  

Thanks in advance! 
Madhutandra