Question number 11-15 based on the passage below.

    Controversial restrictions came into place in England this week, as a month-long lockdown ended. Areas have been placed in one of three tiers. But how was it decided which tier was right for which area? One of the key factors is the rate of coronavirus cases among people over the age of 60. The BBC has analysed the latest figures for areas with both the highest infection rates among the over-60s, and places where the virus is more common in older people than those younger. In the week to 29 November Boston, in Lincolnshire, had the highest number of coronavirus cases among the over-60s. Among all cases, the area had the third highest infection rate in England. Lincolnshire moved into Tier 3 when the England-wide lockdown ended on Wednesday. The county seeing the most areas with the highest infection rates in over-60s was Kent. However, there have been some places where the opposite was true. East Northamptonshire had the largest gap between its infection rates among older and younger people. The rate in older people in the week to 28 November was about 207 cases per 100,000 people, nearly double the rate in under-60s of about 106.

    It is hard to say what causes the virus to spread from one age group to another, as causes can be unique to different parts of the country. Officials said outbreaks in care homes could account for some spikes in older populations but community transmission has also played a large role. The virus has been said to move from younger people to older more often. This could be partly explained by the high number of people over 60 receiving care from those in younger age groups. However, public health teams said the current figures broadly reflected infections acquired as England entered the second national lockdown and could have been a result of last-minute excursions before venues such as pubs and non-essential shops closed.

    Officials have also voiced concerns about the potential impact on hospital capacity if cases rose among the over-60s. Since the pandemic began many hospitals have had fewer beds available for patients, because of extra safety precautious taken to limit the spread of the virus. In many facilities treatment has been divided into Covid-19 and non-Covid-19 zones. Higher numbers of cases among older people in particular would usually mean increased critical care admissions. The knock-on effect of this would be to further reduce hospital capacity to treat non-Covid-19 patients, as hospitals adjusted to cope with the additional strain. The government's recent coronavirus impact assessment said if the NHS in a part of the country were to be overwhelmed - if an area had more patients that needed critical care than it had capacity for - this could result in deaths that may have been prevented, had there been fewer patients.

Based on the passage, phrase knock-on effect in paragraph three means ...