Supplementary appendix

This appendix formed part of the original submission and has been peer reviewed.

We post it as supplied by the authors.

Supplement to: Jefferies S, French N, Gilkison C, et al. COVID-19 in New Zealand

and the impact of the national response: a descriptive epidemiological study.

Lancet Public Health 2020; published online Oct 13. https://doi.org/10.1016/S2468-

2667(20)30225-5.

1

SUPPLEMENTARY

APPENDIX

Table of Contents

Supplementary Table 1: Sensitivity analysis showing features of New Zealand's national COVID-19
epidemiology and response performance over five phases of the study period for confirmed cases only…….2

Supplementary Table 2: Characteristics of COVID-19 cases associated with severe disease outcomes……..4

Supplementary Table 3: Incidence rates of testing per 100,000 person-days at risk in New Zealand over the
study period and by response phase, stratified by population characteristics: sex, ethnicity, age group,
NZDep quintile and District Health Board residence………………………………………………………….6

Supplementary Table 4: Distributions, Maximum Likelihood Estimates with bootstrapped 95%
uncertainty intervals for key time-to-event measures for COVID-19 cases in New Zealand by response
phase………………………………………………………………………………………………………………8

Supplementary Figure 1: Individual symptoms and selected symptom combinations among COVID-19
cases in New Zealand……………………………………………………………………………………...…….10

Supplementary Figure 2: Further features of the New Zealand COVID-19 response timeline……………..11

Supplementary Figure 3: Key time-to-event intervals by response phase……………………………………12

2

Supplementary Table 1: Sensitivity analysis showing features of New Zealand's national COVID-19 epidemiology and response performance over five phases of the
study period for confirmed cases only

Total

Phase 1

2 Feb to 15 Mar

Phase 2

16 Mar to 25 Mar

Phase 3

26 Mar to 10 Apr

Phase 4

11 Apr to 27 Apr

Phase 5

28 Apr to 13 May

EXPOSURE PERIODS

*

New Zealand acquired infection

†

Average estimated daily case infection
rate, cases/day (95% CI)

..

3·6 (3·0–4·3)

31·4 (27·7–35·5)

8·4 (6·9–10·1)

1·4 (0·9–2·2)

0·3 (0·1–0·8)

Average estimated daily case infection
rate, cases/million/day (95% CI),

..

0·7 (0·6–0·9)

6·3 (5·6–7·2)

1·7 (1·4–2·0)

0·3 (0·2–0·4)

0·1 (0·0–0·2)

% rate change from previous phase

..

..

770%

-73%

-83%

-78%

Source of infection, Total n (%)

1153

100

403

100

543

100

174

100

26

100

6

100

Imported case, n, % (95% CI)

520

45 (42–48)

248

61 (56–67)

229

42 (38–47)

40

23 (17–31)

2

7·6 (1·4–33)

1

9·1 (0–100)

Import-related case, n, % (95% CI)

314

27 (25–30)

80

20 (16–25)

175

32 (28–37)

55

32 (24–40)

3

12 (3·6–32)

0

..

Locally-acquired case, n, % (95% CI)

319

28 (25–30)

75

19 (15–23)

139

26 (22–30)

79

45 (37–53)

21

80 (58–92)

5

89 (0–100)

High risk worker, Total n, % (95% CI)

168

15 (13–17)

40

9·9 (7·1–14)

67

12 (9·7–16)

46

26 (20–34)

12

45 (26–66)

3

50 (15–85)

Healthcare worker, n, % (95% CI)

102

8·8 (7·3–11)

26

6·3 (4·2–9·5)

31

5·6 (3·8–8·2)

33

19 (13–26)

11

39 (22–61)

2

37 (8·9–78)

Other

§

, n, % (95% CI)

66

5·7 (4·5–7·2)

14

3·5 (2.0–6·2)

37

6·8 (4·8–9·5)

13

7·2 (3·9–13)

1

5 (0·7–27)

1

0·2 (0–100)

At least one underlying condition, n, %
(95% CI)

243

21 (19–24)

79

20 (16–24)

113

21 (17–25)

43

24 (18–32)

8

31 (15–53)

0

..

Hospitalised, n, % (95% CI)

¥

82

7·1 (5·8–8·7)

29

7·2 (4·9–11)

33

6.0 (4·1–8·7)

15

8·3 (4·7–14)

5

19 (7·3–42)

0

..

ICU admission, n, % (95% CI)

¥

9

0·8 (0·4–1·5)

3

0·8 (0·2–2·6)

5

0·8 (0·3–2·3)

0

0 (0–100)

1

3·6 (0–100)

0

..

Death, n, % (95% CI)

¥

17

1·5 (0·9–2·4)

2

0·1 (0–100)

6

1·1 (0·4–2·7)

9

4·9 (2·4–10)

1

0 (0–100)

0

..

PRESENTATION PERIODS

¶

Confirmed case, n, % (95% CI)

1153

77 (74–79)

111

85 (77–90)

588

85 (83–88)

402

68 (64–71)

40

53 (41–65)

12

80 (52–96)

Basis for case detection, Total (%)

1153

100

111

100

588

100

402

100

40

100

12

100

Contact tracing, n, % (95% CI)

450

39 (36–42)

27

24 (17–33)

171

29 (25–33)

214

53 (48–58)

30

75 (59–87)

8

67 (35–90)

Border, n, % (95% CI)

39

3·4 (2·4–4·6)

3

2·7 (0·6–7·7)

24

4·1 (2·6–6·0)

8

2·0 (0·9–3·9)

3

7·5 (1·6–20)

1

8·3 (0·2–38)

Healthcare presentation, n, % (95% CI)

659

57 (54–60)

81

73 (64–81)

391

66 (63–70)

177

44 (39–49)

7

18 (7·3–33)

3

25 (5·5–57)

Other

‖

, n, % (95% CI)

5

0·4 (0·1–1·0)

0

..

2

0·3 (0–1·2)

3

0·7 (0·2–2·2)

0

..

0

..

3

* Cases were assigned to study exposure periods by sampling incubation periods from a Weibull distribution

15

prior to illness onset (or prior to notification date if no onset

data). Mean case numbers, rates, proportions and confidence intervals are pooled estimates from 1000 replicate incubation samplings, thus capturing uncertainty in incubation
period.
† Excludes imported cases.
§ Includes airline crew, other frontline service workers e.g. police.
¥ Outcomes are not mutually exclusive, i.e. cases could be assigned to more than one of hospitalisation, Intensive Care Unit (ICU) admission, and death. COVID-19 was
reported as the primary cause of death on the COVID-19 case report form for all deceased cases.
¶ Each case was assigned to a study presentation period by date of illness onset (or notification date if no symptom data).
‖ Includes asymptomatic self-referral for testing outside of case definition or contact tracing protocol.
95 % CI = 95 percent confidence intervals.

4

Supplementary Table 2: Characteristics of COVID-19 cases associated with severe disease outcomes

Characteristic

Non-

severe

outcome

(%)

Severe

outcome

¥

(%)

Total cases

in stratum

Crude

β

or age-sex

adjusted analysis

OR (95% CI)

Multivariable

analysis

‡

OR (95% CI)

Total

1387

108

1495

Age group (years)

<1

4

(0·3)

0

(0)

4

..

..

1–4

16

(1·2)

2

(1·9)

18

3·83 (0·81–18·07)

3·13 (0·64–15·23)

5–19

132

(10)

2

(1·9)

134

0·46 (0·11–2·04)

0·42 (0·09–1·89)

20–34

490

(35)

16

(15)

506

Ref

Ref

35–49

285

(21)

13

(12)

298

1·4 (0·66–2·95)

1·2 (0·55–2·63)

50–64

311

(22)

29

(27)

340

2·86 (1·53–5·34)

2·72 (1·40–5·30)

65–79

128

(9·2)

28

(26)

156

6·70 (3·52–12·76)

5·42 (2·54–11·57)

≥80 years

21

(1·5)

18

(17)

39

26·25 (11·76–58·58)

8·25 (2·59–26·31)

Sex

Female

773

(56)

58

(54)

831

Ref

Ref

Male

614

(44)

50

(46)

664

1·09 (0·73, 1·61)

0·86 (0·55–1·35)

Ethnicity

European or Other

1012

(73)

75

(69)

1087

Ref

Ref

Māori

122

(8·8)

10

(9·3)

132

1·36 (0·65–2·85)

1·28 (0·57–2·89)

Pacific peoples

70

(5·0)

9

(8·3)

79

3·07 (1·38–6·85)

2·76 (1·14–6·68)

Asian

167

(12)

14

(13)

181

2·08 (1·1–3·95)

2·15 (1·10–4·20)

Unknown

16

(1·2)

0

(0)

16

-

-

NZDep quintile

1

326

(24)

16

(15)

342

Ref

Ref

2

331

(24)

28

(26)

359

1·79 (0·93–3·44)

1·72 (0·89–3·33)

3

247

(18)

12

(11)

259

0·98 (0·44–2·15)

0·81 (0·36–1·82)

4

254

(18)

24

(22)

278

1·77 (0·89–3·51)

1·35 (0·66–2·73)

5

149

(11)

20

(19)

169

2·36 (1·13–4·95)

1·43 (0·65–3·16)

High-risk occupation
or Aged Residential
Care residency

High-risk worker

±

158

(11)

11

(10)

169

1·31 (0·66–2·61)

..

Healthcare worker

±

139

(10)

9

(8·3)

148

1·22 (0·58–2·57)

..

Aged Residential Care
resident

24

(1·7)

23

(21)

47

3·86 (1·59–9·35)

..

Rural dweller

Rural resident

223

(16)

14

(13)

237

0·86 (0·47–1·59)

..

Source of infection

Imported

542

(39)

30

(28)

572

Ref

..

Import-related

432

(31)

24

(22)

456

0·92 (0·51–1·64)

..

Locally-acquired

413

(30)

54

(50)

467

2·32 (1·40–3·82)

..

Exposure Phase

†

2 Feb to 15 Mar

437

(32)

32

(29)

469

Ref

..

16 Mar to 25 Mar

628

(45)

39

(36)

667

0·84 (0·48–1·48)

..

26 Mar to 10 Apr

276

(20)

28

(26)

304

1·38 (0·77–2·48)

..

11 Apr to 27 Apr

38

(2·7)

9

(8·3)

47

3·08 (1·22–7·77)

..

5

28 Apr to 13 May

7

(0·5)

1

(0.9)

8

..

..

Underlying condition

€

At least one reported
underlying condition

251

(18)

43

(40)

294

1·81 (1·16–2·83)

..

Cardiovascular disease
(including
hypertension)

92

(6·6)

20

(19)

112

1·28 (0·71–2·31)

..

Diabetes

46

(3·3)

11

(10)

57

1·73 (0·82–3·64)

..

Chronic lung condition

118

(8·5)

11

(10)

129

1·12 (0·56–2·23)

..

Malignancy

11

(0·8)

2

(1·9)

13

2·36 (0·52–10·79)

..

Immunodeficiency,
including HIV

5

(0·4)

0

(0)

5

..

..

Liver Disease

4

(0·3)

1

(0·9)

5

..

..

Chronic neurological
or neuromuscular
disease

5

(0·4)

8

(7·4)

13

..

..

Renal failure

3

(0·2)

4

(3·7)

7

..

..

Pregnant

13

(0·9)

3

(2·8)

16

..

..

Post-partum

0

(0)

0

(0)

0

..

..

¥

Hospitalisation and/or death. COVID-19 was reported as the primary cause of death on the COVID-19 case

report form for all deceased cases.

ß

Crude odds ratios are presented for age, sex, source of infection and exposure phase variables only. Due to

significant confounding by age, all other odds ratios are presented with adjustment for age and sex.

‡

Multivariable adjustment for age, sex, ethnicity, Aged Residential Care facility residency, socio-economic

status and having at least one underlying condition.

±

High-risk workers who were imported cases (i.e. infection not acquired while working in New Zealand) were

excluded from this analysis. Healthcare worker is a subset of the high-risk worker group.

†

Cases were assigned to study exposure periods by sampling incubation periods from a Weibull distribution

15

prior to illness onset (or prior to notification date if asymptomatic or onset unknown). Mean case numbers,
proportions, odds ratios and confidence intervals are pooled estimates from 1000 replicate incubation samplings,
thus capturing uncertainty in incubation period.

€

There was insufficient data for precise estimates of risk associated with individual underlying conditions and

analyses were not performed for conditions with <20 total observations.
Complete observations were available for 1495 cases.
95% CI = 95 percent confidence intervals.

6

Supplementary Table 3: Incidence rates of testing per 100,000 person-days at risk in New Zealand over
the study period and by response phase, stratified by population characteristics: sex, ethnicity, age group,
NZDep quintile and District Health Board residence

Characteristic

Phase 1 incidence
rate (95% CI)

Phase 2 incidence
rate (95% CI)

Phase 3 incidence
rate (95% CI)

Phase 4 incidence
rate (95% CI)

Phase 5 incidence
rate (95% CI)

Sex

Female

0·5 (0·5-0·6)

30·6 (29·9-31·2)

66·7 (65·9-67·5)

90·6 (89·7-91·5)

129·6 (128·5-130·8)

Male

0·5 (0·4-0·5)

23·9 (23·3-24·6)

46·2 (45·6-46·9)

65·4 (64·7-66·2)

89·3 (88·3-90·2)

Ethnicity

Asian

1·0 (0·9-1·1)

20·9 (19·9-21·9)

39·3 (38·2-40·4)

43·0 (41·9-44·1)

77·0 (75·4-78·5)

European or Other

0·4 (0·4-0·5)

29·4 (28·8-30·0)

59·8 (59·2-60·5)

82·8 (82·0-83·6)

110·7 (109·8-111·7)

Māori

0·2 (0·2-0·3)

20·2 (19·3-21·3)

52·9 (51·7-54·2)

80·8 (79·3-82·3)

117·3 (115·4-119·2)

Pacific

0·5 (0·3-0·6)

30·4 (28·6-32·4)

67·7 (65·4-70·0)

107·6 (104·8-110·4)

154·0 (150·6-157·4)

Age group

1 year

0·3 (0·1-0·5)

2·9 (1·7-4·6)

6·2 (4·7-7·9)

8·6 (6·9-10·5)

9·8 (8·0-12·0)

1 to 4 years

0·5 (0·4-0·6)

16·4 (14·8-18·0)

26·5 (24·9-28·2)

34·3 (32·5-36·1)

35·3 (33·5-37·2)

5 to 19 years

0·2 (0·2-0·3)

12·5 (11·8-13·3)

21·6 (20·9-22·4)

29·2 (28·4-30·1)

41·5 (40·5-42·6)

20 to 34 years

0·7 (0·6-0·7)

39·7 (38·6-40·9)

64·9 (63·7-66·1)

74·4 (73·1-75·6)

116·9 (115·3-118·5)

35 to 49 years

0·7 (0·6-0·7)

36·4 (35·2-37·7)

77·2 (75·7-78·6)

99·8 (98·2-101·4)

140·2 (138·3-142·1)

50 to 64 years

0·5 (0·5-0·6)

31·4 (30·3-32·6)

76·6 (75·1-78·0)

112·0 (110·3-113·6)

161·6 (159·5-163·7)

65 to 79 years

0·5 (0·4-0·6)

19·4 (18·3-20·6)

55·3 (53·9-56·9)

96·2 (94·3-98·2)

122·1 (119·9-124·3)

≥80 years

0·5 (0·3-0·7)

12·6 (11·0-14·3)

51·4 (48·8-54·1)

108·0 (104·3-111·7)

114·2 (110·4-118·2)

NZDep quintile

1

0·5 (0·5-0·6)

30·7 (29·7-31·8)

52·4 (51·3-53·5)

66·5 (65·3-67·8)

92·6 (91·1-94·1)

2

0·5 (0·5-0·6)

27·3 (26·3-28·3)

50·8 (49·7-51·9)

65·8 (64·6-67·0)

95·1 (93·6-96·6)

3

0·5 (0·4-0·6)

25·0 (24·1-26·0)

53·8 (52·6-54·9)

70·7 (69·4-72·0)

100·7 (99·2-102·3)

4

0·4 (0·4-0·5)

23·6 (22·7-24·6)

55·7 (54·5-56·9)

78·5 (77·1-79·8)

113·9 (112·3-115·6)

5

0·4 (0·3-0·4)

22·9 (21·9-23·8)

58·3 (57·1-59·5)

93·7 (92·3-95·2)

125·1 (123·3-126·9)

District Health Board

Auckland

1·3 (1·2-1·5)

42·2 (40·5-44·0)

56·0 (54·5-57·6)

64·0 (62·3-65·6)

109·8 (107·6-112·0)

Bay of Plenty

0·1 (0·0-0·2)

14·8 (13·3-16·4)

48·7 (46·5-50·9)

90·4 (87·5-93·3)

77·7 (75·0-80·6)

Canterbury

0·3 (0·3-0·4)

16·5 (15·5-17·6)

42·5 (41·2-43·9)

69·8 (68·2-71·5)

87·5 (85·6-89·4)

Capital and Coast

0·3 (0·2-0·4)

34·1 (32·1-36·2)

60·0 (57·9-62·2)

75·8 (73·5-78·1)

92·0 (89·4-94·6)

Counties Manukau

0·6 (0·5-0·7)

30·8 (29·4-32·3)

62·0 (60·4-63·7)

86·5 (84·7-88·4)

127·6 (125·3-129·9)

Hawke's Bay

0·2 (0·1-0·4)

19·6 (17·5-21·8)

59·0 (56·1-62·0)

82·5 (79·1-85·9)

98·5 (94·8-102·4)

Hutt Valley

0·2 (0·1-0·4)

22·2 (19·9-24·7)

58·3 (55·2-61·4)

83·6 (80·1-87·2)

87·9 (84·1-91·7)

Lakes

0·2 (0·1-0·3)

15·5 (13·2-18·0)

58·7 (55·1-62·3)

74·6 (70·8-78·6)

93·3 (88·8-97·9)

MidCentral

0·2 (0·1-0·3)

12·8 (11·3-14·6)

38·0 (35·8-40·3)

76·6 (73·5-79·7)

80·6 (77·4-84·0)

Nelson Marlborough

0·4 (0·2-0·5)

23·3 (20·9-25·9)

39·0 (36·6-41·6)

63·8 (60·7-66·9)

107·9 (103·8-112·2)

Northland

0·3 (0·2-0·4)

31·2 (28·7-33·9)

56·9 (54·2-59·7)

69·4 (66·5-72·4)

136·0 (131·8-140·3)

South Canterbury

0·2 (0·0-0·4)

16·9 (13·8-20·6)

47·2 (43·0-51·8)

92·9 (87·0-99·0)

105·8 (99·4-112·5)

Southern

0·3 (0·3-0·5)

22·4 (20·8-24·1)

67·1 (64·9-69·3)

80·7 (78·4-83·1)

108·1 (105·3-110·9)

Tairawhiti

0·1 (0·0-0·4)

17·4 (13·9-21·5)

39·8 (35·5-44·4)

196·4 (187·0-206·2)

134·6 (126·6-143·0)

Taranaki

0·1 (0·0-0·3)

17·8 (15·5-20·3)

36·0 (33·4-38·8)

75·7 (72·0-79·5)

137·3 (132·1-142·7)

Waikato

0·2 (0·1-0·2)

31·0 (29·4-32·8)

76·3 (74·3-78·4)

86·0 (83·9-88·2)

129·4 (126·7-132·1)

Wairarapa

0·3 (0·1-0·6)

52·5 (46·1-59·5)

84·7 (78·2-91·7)

67·6 (62·0-73·7)

76·4 (70·2-83·0)

Waitemata

0·9 (0·8-1·0)

31·6 (30·2-33·0)

58·0 (56·5-59·5)

72·2 (70·6-73·8)

121·1 (119·0-123·3)

7

West Coast

0·1 (0·0-0·4)

12·6 (9·1-17·1)

62·6 (56·0-69·8)

68·2 (61·5-75·5)

75·4 (68·1-83·3)

Whanganui

0·1 (0·0-0·4)

7·6 (5·7-10·1)

31·8 (28·5-35·4)

98·2 (92·4-104·2)

190·4 (182·1-199·1)

Incidence rates and 95 percent confidence intervals (95% CI) presented as tests per 100,000 person-days at risk.

8

Supplementary Table 4: Distributions, Maximum Likelihood Estimates with bootstrapped 95%
uncertainty intervals for key time-to-event measures for COVID-19 cases in New Zealand by response
phase

*

a) illness onset to notification date intervals in days (confirmed and probable cases)

‡

Onset to report date

Distribution

Shape

Rate

Mean

5% Quantile

50%

Quantile

95%

Quantile

Overall

Gamma

1·1

0·2

6·7

0·5

4·9

19·3

95% CI

(1·1, 1·2)

(0·2, 0·2)

(6·4, 7·1)

(0·4, 0·5)

(4·6, 5·1)

(18·3, 20·4)

Phase 1

3·1

0·3

10·8

3·0

9·7

22·5

95% CI

(2·5, 3·9)

(0·2, 0·4)

(9·8, 11·9)

(2·4, 3·7)

(8·8, 10·7)

(19·9, 25·0)

Phase 2

1·7

0·2

7·7

1·1

6·3

19·2

95% CI

(1·6, 1·9)

(0·2, 0·2)

(7·2, 8·1)

(0·9, 1·3)

(5·9, 6·7)

(17·9, 20·4)

Phase 3

0·9

0·2

5·2

0·2

3·4

16·2

95% CI

(0·8, 1.0)

(0·2, 0·2)

(4·8, 5·7)

(0·1, 0·3)

(3·1, 3·8)

(14·7, 17·8)

Phase 4

0·8

0·3

2·7

0·1

1·7

9·0

95% CI

(0·6, 1·0)

(0·2, 0·4)

(2·1, 3·6)

(0·0, 0·2)

(1·2, 2·2)

(6·6, 12·0)

b) illness onset to isolation date intervals in days (confirmed and probable cases)

§

Time period

Distribution

Mean

SD

5% Quantile

50%

Quantile

95%

Quantile

Overall

Normal

1·2

6·5

-9·6

11·9

95% CI

(0·8, 1·5)

(6·3, 6·8)

(-10·1, -9·0)

(11·4, 12·4)

Phase 1

7·2

5·5

-1·7

16·3

95% CI

(6·3, 8·2)

(4·8, 6·1)

(-3·2, -0·2)

(14·9, 17·6)

Phase 2

2·4

5·4

-6·6

11·3

95% CI

(1·9, 2·8)

(5·2, 5·7)

(-7·2, -6.0)

(10·7, 11·9)

Phase 3

-1·1

6·1

-11·2

9·0

95% CI

(-1·6, -0·6)

(5·8, 6·5)

(-11·9, -10·4)

(8·3, 9·8)

Phase 4

-2·7

8·3

-16·4

11·0

95% CI

(-4·7, -0·8)

(7·0, 9·7)

(-19·5, -13·4)

(7·9, 13·9)

c) illness onset to case confirmation intervals in days

†¶

Onset to diagnosis

Distribution

Shape

Rate

Mean

5% Quantile

50%

Quantile

95%

Quantile

Overall

Gamma

1·8

0·3

7·1

1·1

5·8

17·4

95% CI

(1·6, 1·9)

(0·2, 0·3)

(6·8, 7·4)

(1·0, 1·2)

(5·5, 6·1)

(16·5, 18·3)

Phase 1

4·3

0·4

10·6

3·8

9·8

20·2

95% CI

(3·3, 5·7)

(0·3, 0·5)

(9·7, 11·6)

(3·1, 4·6)

(8·9, 10·7)

(18·1, 22·5)

Phase 2

2·3

0·3

7·5

1·5

6·4

17·1

95% CI

(2·0, 2·6)

(0·3, 0·3)

(7·1, 7·9)

(1·4, 1·8)

(6·0, 6·8)

(16·0, 18·1)

Phase 3

1·5

0·3

5·9

0·7

4·7

15·3

95% CI

(1·4, 1·8)

(0·2, 0·3)

(5·5, 6·5)

(0·6, 0·9)

(4·3, 5·1)

(13·9, 16·8)

Phase 4

1·4

0·6

2·6

0·3

2·0

6·8

95% CI

(1·0, 2·3)

(0·3, 1·0)

(1·9, 3·4)

(0·1, 0·6)

(1·5, 2·8)

(4·9, 9·2)

*Observations were too small for Phase 5 calculations.

‡

Observations available for 1468 cases.

§

Observations available for 1463 cases.

9

¶

Observations available for 1115 cases.

†

Sensitivity analysis using onset to confirmation interval (i.e. excluding probable cases) found no significant

differences in timeliness except the average onset to notification interval was shorter in Phase 3, which had the
highest proportion of probable cases.
95% CI = 95 percent uncertainty intervals.
Negative values represent days prior to illness onset.

10

Supplementary Figure 1: Individual symptoms and selected symptom combinations among COVID-19
cases in New Zealand

Data were available for 1472 of 1478 symptomatic cases. Proportions are presented with 95 percent confidence
intervals.

11

Supplementary Figure 2: Further features of the New Zealand COVID-19 response timeline

A. Daily international passenger arrivals at national Ports of Entry and Government Response

Stringency Index for New Zealand

B. Daily percentage change in national population mobility from baseline prior to the first national

movement restrictions

Supplementary figure 2B dashed-line represents last day of baseline period of national population
mobility prior to first national movement restriction on 16 March.

12

Supplementary Figure 3: Key time-to-event intervals by response phase

A. COVID-19 case illness onset to notification date intervals

B.

COVID-19 case onset to isolation date intervals

Distribution parameters were calculated using maximum likelihood estimation. Uncertainty in the parameters
were estimated by bootstrapping. Phase 5 was excluded from analyses due to the small numbers. Further detail is
provided in supplementary table 4. Complete onset to notification observations were available for 1468 cases, and
1463 cases for onset to isolation analysis. 95% UI = 95 percent uncertainty intervals. Negative values represent
days prior to illness onset.