On 16 Sept 2020, Cochrane published an updated special collection of systematic and rapid reviews focused on public health measures to control and prevent the spread of COVID-19. The special collection of reviews from Cochrane contains three rapid reviews of the evidence on measures that aim to prevent potentially infected people from transmitting the virus to healthy people.

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SARS-CoV-2, the new virus that has spread quickly throughout the world causes coronavirus disease 2019 (COVID-19). Most infected people either experience no symptoms or suffer mild, flu-like symptoms, but some become seriously ill and may die. According to www. worldometers.info/coronavirus/, as of 17 September 2020, there were 30,042,299 COVID-19 cases and 945, 164 deaths globally.

Why do we consider this disease as special? Presently, we do not have a vaccine that can stop people from catching COVID-19. So we need other ways of slowing its spread. Recently Cochrane published a collection of reviews on public health measures to control the pandemic.

Many countries have adopted combinations of these measures and are faced with the challenge of easing or strengthening each of these measures over the course of the pandemic. Discerning sections of the public including Members of Parliament, decision makers at the highest levels NGOs, besides health care workers and other stakeholders must read Cochrane reviews. Representative multidisciplinary expert groups can produce actionable plans in light of these reviews so that the nation can get full benefits.

Public health measures

Quarantine, travel-related controls and universal screening are three different public health measures which help to slow down the spread of the disease

How do the different stake-holders get the insights on these measures from detailed analysis of existing evidence collected from peer reviewed scientific papers, clinical trials, case histories, cohort studies, case-control-studies, case series, time series, interrupted time series, and mathematical modelling studies among others?

We must urgently learn how effective these measures are. Proper insights will help responsible authorities, health care workers and the members of the public to spend resources optimally to control the spread of the disease.

That is where Cochrane reviews come in.

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Cochrane Reviews

“Cochrane is a global independent network of researchers, professionals, patients, carers and people interested in health. Cochrane produces reviews which study all of the best available evidence generated through research and make it easier to inform decisions about health. These are called systematic reviews. Cochrane is a not-for profit organisation with collaborators from more than 130 countries working together to produce credible, accessible health information that is free from commercial sponsorship and other conflicts of interest,” the press release from Cochrane asserted.

Cochrane’s “work is recognised as representing an international gold standard for high quality, trusted information.” It is globally respected. The international agencies such as the WHO keep track of these reviews; in some cases they request such reviews by Cochrane.

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Special collection of systematic and rapid reviews by Cochrane

The special collection of reviews from Cochrane contains three rapid reviews of the evidence on measures that aim to prevent potentially infected people from transmitting the virus to healthy people.

A press release from Cochrane issued on 16 September 2020, listed the measures thus (verbatim):

• Quarantine, where healthy people are separated from other healthy people in case they might have the virus because they either have had contact with a case or have travelled from an area with high transmission rates
• Universal screening of people not seeking care for symptoms, either the general population or a targeted population based on their occupation, for example, healthcare workers in hospitals and nursing homes.
• Travel-related control measures, such as border closures, partial travel restrictions and entry/exist screening

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Conclusions of Cochrane from the studies

Does quarantine, control coronavirus (COVID-2019) either alone or in combination with other public health measures?

There is low-certainty evidence from mathematical modelling studies which consistently indicate that quarantine is important in reducing the number of people with COVID-19, but the size of the reduction is uncertain. Estimates range from a minimum reduction in the number of people with the disease of 44%, and a maximum reduction of 96%.’

The lead author Barbara Nussbaumer-Streit (Danube University Krems, Austria) of the review on effectiveness of quarantine revealed that they published the first version of this review in April 2020. Since then 22 additional studies on quarantine for COVID-19 have become available.

“While the number of studies has increased significantly in a short space of time, the evidence base is still limited because most studies on COVID-19 are mathematical modelling studies that make different assumptions on important model parameters. The evidence suggests that implementation of quarantine early on in a pandemic and combining quarantine with other public health measures such as physical distancing, can help slow the spread of COVID-19. However, it is difficult to determine what combination of measures is the best to reduce the number of cases and deaths,” she added.

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How effective is screening for COVID-19?

The reviewers stated that screening aims to identify a condition in people who may not be showing any symptoms. Some COVID‐19 patients appear healthy or have only mild symptoms. In order to control the spread of the disease, authorities must identify infected people so they can stay away from others and seek appropriate care. Incorrectly identifying COVID‐19 in healthy people could lead to unnecessary self‐isolation and further tests. Incorrectly identifying no infection in infected people could spread the virus.

Screening for COVID‐19 can include temperature checks, or asking about international travel or contact with COVID‐19 cases, or rapid tests. Screening can occur over the telephone, online, or in person, in homes, clinics, workplaces, airports or schools.

Cochrane wanted to identify: the benefits and negative effects of screening apparently healthy people for COVID‐19 infection; they wanted to know whether screening can identify those with and without the virus correctly.

Since the reviewers wanted rapid answers, they shortened some steps of the normal Cochrane Review process. However, they are confident these changes do not affect the overall conclusions.

Some important observations:

The reviewers located 22 studies; 17 assessed people (cohort studies) and five were computer‐generated models (modelling studies). Studies took place in USA, Europe, and Asia. Two modelling studies reported on the benefits and negative effects of screening. One suggested that asking about symptoms at airports may slightly slow, but not stop, the importation of infected people. Another model reported that weekly or biweekly screening of healthcare workers may reduce transmission to patients and other healthcare workers in emergency departments. No studies reported on negative effects of screening.

The following observations of the reviewers- most of them reproduced verbatim- are crucial.

Seventeen cohort studies and three modelling studies reported on whether screening can correctly identify those with and without the virus. Studies varied widely in the baseline level of COVID‐19, settings, and methods. All cohort studies compared screening strategies to a ‘gold standard’ test called RT‐PCR.

1. All screening strategies (17 studies, 17,574 people), incorrectly identified:
   1. Between 20 and 100 out of 100 infected people as healthy;
   2. Between 0 and 38 people out of 100 healthy people as infected
2. Asking about symptoms (13 studies, 16,762 people ), incorrectly identified:
   1. Between 40 to 100 out of 100 infected people as healthy;
   2. Between 0 to 34 out of 100 healthy people as infected
3. Temperature measurements, asking about international travel, exposure to known infected people and exposure to known or suspected infected people (6 studies, 14,741 people), incorrectly identified:
   1. Between 77 and 100 out of 100 infected people as healthy
   2. Between 0 and 10 out of 100 healthy people as infected
4. Asking about symptoms plus temperature measurement (2 studies, 779 people), incorrectly identified:
   1. Between 31 and 88 out of 100 infected people as healthy
   2. Between 0 to 10 people out of 100 healthy people as infected

There was insufficient evidence from two small studies on rapid laboratory tests and repeated symptom assessment to tell how accurate they were in identifying healthy and infected people.

Modelling studies: Three studies modelled entry and exit screening in airports. One study missed 70% of infected travellers. Another detected 90% of infections, but used an unrealistic scenario. The third used very unreliable methods so we cannot use evidence from this study.

How confident are we in the results of the studies?

The reviewers’ confidence in these findings is limited because most studies did not describe their screening methods clearly, some found very few cases of infections and the types of participants and settings varied greatly, making it difficult to judge whether the results apply broadly.

This review highlights the uncertainty and variation in accuracy of screening strategies.

Observational studies evaluated different screening strategies, mainly screening people once rather than repeatedly, and involved either asking about symptoms, international travel, or exposure to a known or suspected case, performing temperature checks, or a rapid point-of-care test. Some studies combined screening for symptoms and temperature checks. With any screening strategy a high proportion of infected individuals may be falsely identified as negative. Future population-based screening studies will add substantially to our understanding of the effectiveness and accuracy of screening for COVID-19.

Lead author Meera Viswanathan (RTI International, North Carolina, USA) admitted that they are unsure whether combined screenings, repeated symptom assessment, or rapid laboratory tests are useful.

“Because screening can miss people who are infected, public health measures such as face coverings, physical distancing, and quarantine for those who may have contact with an infected person, continue to be very important.” she cautioned.

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Can travel-related control measures contain the spread of the COVID-19 pandemic?

Cochrane carried out this review as per the request made by the WHO in May 2020. From thousands of records collected by searching relevant databases, they found 385 records to be potentially relevant and screened them at the full‐text stage; of these, 40 records met the eligibility criteria and the authors included them in the review. These represent 36 unique studies, as four records assessed interventions already addressed by other records

The 159 page review showed that there is very low-certainty evidence from modelling studies, suggesting that when implemented at the beginning of an outbreak, cross-border travel restrictions may lead to a reduction in the number of new cases of between 26% to 90%. Observational studies of entry and exit screening evaluated different combinations of symptom-based screening, single (and rarely repeated) PCR swab testing and observation during quarantine.

There is very low-certainty evidence that suggests that the proportion of cases detected at the border ranged from 0% to 75%. The reviewers noted that entry and exit symptom screening measures on their own are not likely to be effective in detecting enough cases to prevent new cases becoming established within the protected region. They found that a combination of approaches including symptom screening, quarantine, observation and PCR testing may help to more accurately identify positive cases.

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Effective action may take time

The present Cochrane reviews give actionable information on the effectiveness of these measures; it may take time for society at large to benefit from them as focussed implementation of actions from the lessons learnt from the Cochrane reviews needs dedicated follow up from many agencies. However, we cannot wait more, as the tiger is at our doorsteps!

The State, Municipal and Central agencies are making every effort to contain the pandemic. Members of the public have a greater responsibility to ensure slowing down the infection by isolation (like quarantine, but for people who tested positive for COVID-19) and physical distancing (people without symptoms keep a distance from each other) and the use of appropriate personal protective equipment such as masks and regular hand washing to ensure that the virus picked up by persons from virus- carrying droplets does not reach their mouth, nose or eyes. Comply with the relevant steps scrupulously.

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Suggestion from Cochrane

Cochrane suggested that in order to maintain the best possible balance of public health measures,

“Decision-makers must constantly monitor their outbreak situation and assess the impact of the measures implemented. Future research will help to disentangle the effects of these diverse prevention and control measures and will help determine which measures or combinations of measures may work best while minimising the harms to our communities.”

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The take-home message is that all stakeholders must read the Cochrane reviews and modify the control measures in light of the important findings of Cochrane. The reviews always contain a plain-language summary meant for public

Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

Dr. K S Parthasarathy is a freelance science journalist and a former Secretary of the Atomic Energy Regulatory Board.